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Metal oxides have been widely studied, due to the many applications they are useful for. Their diverse properties, for example supercapacitance, piezoelectricity, semiconductivity and superconductivity have meant that research into metal oxides for application has been vast. Within this body of work, synthesis routes to manipulate the structure of several metal oxides were studied. These oxides were: Dy2Ti2O7, Gd2Ti2O7, CuBi2O4, CO3O4, NiO, α-Fe2O3 and several phases of strontium niobate. Utilising a biotemplated approach, morphology control and application was the key focus of the project.

This thesis describes the synthesis and characterisation of phases related to schafarzikite (FeSb\(_2\)0\(_4\)). A range of Co\(_1\)\(_-\)\(_x\)Fe\(_x\)Sb\(_2\)\(_-\)\(_y\)Pb\(_y\)O\(_4\) (where x = 0, 0.25, 0.50 and 0.75; y = 0-0.75) compounds have been synthesised and characterised by a variety of techniques e.g. neutron powder diffraction (NPD), and thermogravimetric analysis. The refined lattice parameters for all compounds range between a = 8.4492(2) Å - 8.5728(2) Å and c = 5.9170(1) Å - 6.0546(2) Å (NPD, 300 K). The magnetic structures of Co\(_0\)\(_.\)\(_2\)\(_5\)Fe\(_0\)\(_.\)\(_7\)\(_5\)Sb\(_2\)O\(_4\) and Co\(_0\)\(_.\)\(_5\)\(_0\)Fe\(0\)\(_.\)\(_5\)\(_0\)Sb\(_2\)O\(_4\) have been shown to possess dominant A- type ordering as a result of overriding direct exchange interactions between intrachain transition metal cations, whilst all other phases show dominant C- type ordering consistent with 90˚ superexchange. Unusual negative susceptibility is seen and explained in several samples including CoSb\(_2\)O\(_4\). All phases are shown to display canted antiferromagnetic magnetic order. Oxidised intermediates are formed and characterised for the first time. This has been critically linked to the presence of Fe\(^2\)\(^+\) within these phases. There is evidence to suggest the excess oxygen is a peroxide and/or superoxide species. The synthesis of LiSbO\(_2\) is described and its structure determined: P2\(_1\)\(_/\)\(_c\) symmetry with a = 4.8550(3) Å, b = 17.857(1) Å, c = 5.5771(4) Å, β = 90.061(6)˚. Its electrical and thermal properties are described.

This thesis presents computational work on the structures, characterisation and optical properties of homogeneous gold nanoclusters, and gold-containing bimetallic nanoalloys. An introductory overview of nanoscience is followed by four results chapters in which various computational methods are applied to elucidate properties that are not fully understood; from these results areas for future development, and application, are identifed. Chapter 2 looks at structural motif preference as a function of composition and size for Au and Pd. Bimetallic (AuPd)_N particles are further studied, with thermodynamic preference found for Au_shellPd_core configurations with a monolayer Au shell. Chapter 3 discusses the development and implementation of a genetic algorithm designed to aid the determination of the structures of small nanoclusters from images taken with a scanning transmission electron microscope. The implementation of a search method proves efficient at identifying high-symmetry test clusters, and shows promise for further application to the identification of cluster structure from experimental images. Chapter 4 contains a first-principles study of Au₁₆ deposited on a graphite substrate. We introduce surface defects to see their influence on the nanocluster structure, as well as testing for potential catalytic applications. Finally, Chapter 5 looks at the optical response of monometallic and bimetallic nanoparticles. Surface plasmon resonance spectra are calculated for a variety of geometries, compositions and chemical ordering. The greatest influence on the extinction spectra is attributed to the particle shape and its environment.

Some low-valent, three-coordinated β-diketiminato heavy group 14 metal complexes have been synthesised and their reactions examined. Initially, our attention is focused on several β-diketiminatolead(II) alkoxides. The lead(II) alkoxides show different basic and nucleophilic reactivities from transition metal analogues. For example, the reaction between the lead(II) tert-butoxide and methyl iodide proceeds only under forcing conditions to give the lead(II) iodide and methyl tert-butyl ether. However, facile reversible carbon dioxide insertion into the lead-oxygen bond is observed. To investigate the steric effect of the bulky β-diketiminato ligand, compounds with various aromatic groups attached to nitrogen have been made. When either [(BDIPh)PbCl] (BDIPh = [HC{C(Me)N(C6H5)}2]−) or [(BDIIPP)PbCl] (BDIIPP = [HC{C(Me)N(4-iPrC6H4)}2]−) was treated with potassium tert-butoxide, the reactions gave the unexpected bis[β-diketiminato]lead(II) complexes. However, treatment of [(BDIDMP)PbCl] (BDIDMP = [HC{C(Me)N(2,6-Me2C6H3)}2]−) with AgOTf led to the expected β-diketiminatolead(II) triflate. These results suggest that the ortho-substituent on the N-aryl groups in the β-diketiminato ligand plays an important role in influencing the formation of bis[β-diketiminato]lead(II) complexes. A series of β-diketiminato heavy group 14 metal phosphanides was synthesised. The phosphorus is pyramidally coordinated in the compounds containing diphenyl- or dicyclohexylphosphanido ligands. In contrast, the geometry at phosphorus is planar in the germanium(II) and tin(II) bis(trimethylsilyl)phosphanides. The phosphorus in the lead(II) bis(trimethylsilyl)phosphanide is pyramidally coordinated. The observed conformations may be explained by the steric congestion from the β-diketiminato ligand and electronic effects in the phosphanido ligand. Reactions of the phosphanido complexes with one equivalent of elemental chalcogen give phosphinochalcogenoito complexes. Further reaction with elemental chalcogen gives phosphinodichalcogenoato complexes. In contrast, treatment of the germanium(II) dicyclohexylphosphanide with elemental chalcogen leads to the formation of germanium(IV) chalcogenide. The presence of NMR-active nuclei in these complexes makes possible detailed spectroscopic analysis.

3-Nitrophthalic acid 2.04 was transformed into 2.10 in 38% yield. Vinylglycine derivative was synthesised from D-Methionine 2.12 in 42% yield. (For image see abstract in pdf) Compounds 2.10 and 2.16 were coupled using Grubbs' 2nd generation catalyst creating 2.25. Unfortunately attempts to oxidise the benzylic position were unsuccessful. (For image see abstract in pdf) An alternative approach was investigated using diene 2.40 derived from a precursor to 2.10 and allyl bromide 2.35. Attempts to displace bromide under anionic conditions were futile. The use of palladium formed conjugated dieneamine 2.65. (For image see abstract in pdf) Deprotection, oxidation and elaboration of 2.10 prior to cross metathesis allowed the synthesis of 2.114, which when subjected to radical conditions, formed a diastereomeric mixture of 2.220. (For image see abstract in pdf).

One commercial application of emissive lanthanide complexes is in fluoroimmunoassays, which combine FRET with time-resolved detection of emission to glean information on biological interactions. Herein the development of highly emissive europium complexes to act as FRET donors in this process is described. Each complex reported in this thesis incorporates a coordinating ligand, which chelates to the metal ion centre, and a sensitising group, capable of populating the europium excited state. To maximise the molar extinction coefficient and emission quantum yield of the complexes, variation of the ligand and sensitising group, was addressed. An initial study into the use of 3-azaxanthone as a sensitising group was undertaken. A constitutional isomer of this chromophore is known to sensitise europium emission. The new system was developed to allow inclusion of four sensitising groups per complex, with a view to maximising the overall molar extinction coefficient. The resulting systems showed little improvement upon previously reported complexes and a new chromophore was devised, which possesses a much higher molar extinction coefficient and is able to sensitise europium emission efficiently. A series of complexes was synthesised in which the chelating ligand was varied to investigate the effect upon the photophysical properties. The complex with the properties best suited to the FRET application combines phenylphosphinate donating groups with a high degree of symmetry about the metal ion centre. The ability of this complex to withstand quenching of emission by a number of competitive anions and cations was explored and it was found that the complex possesses high kinetic stability. By bringing together the favourable photophysical properties imparted by the phenylphosphinate ligand and the high molar extinction coefficient of the new sensitising group, a final europium complex was synthesised with an extraordinarily high brightness, defined as the product of the emission quantum yield and molar extinction coefficient. This final complex met the specification for a FRET donor set out at the beginning of the project.

Luminescent transition metal complexes are of interest due to their applications in areas such as organic light-emitting devices (OLEDs), solar cells and biological probes and sensors. The use of heavy transition metals promotes phosphorescent emission from the triplet state. In OLEDs, this enables the quantum efficiency of devices to reach a theoretical maximum of 100 % through harvesting photons from both singlet and triplet excited states. The synthesis of cyclometallated N^C^N-coordinated iridium(III) complexes and two representative rhodium(III) analogues, based upon a series of isomeric 1,3-(diquinolyl)benzene ligands, is presented. The d6 complexes take the form M(N^C^N)(X^Y)Z, where X^Y denotes a bidentate ligand binding through N^C- or N^N-coordination, and Z denotes a monodentate ligand, such as chloride. Platinum(II) complexes containing terdentate ligands, of the form Pt(N^C^N)Cl, have also been investigated. All complexes are luminescent at room temperature and at 77 K, emitting in the red-to-yellow region of the visible spectrum. The photophysical properties are interpreted with the aid of electrochemical and computational analyses. Preliminary results from incorporation of three of the complexes into OLEDs are described. In addition, an iridium phosphor used in conjunction with a blue emitter produces a white device which displays excellent white light characteristics. The platinum(II) complex of 1,3-di(8-quinolyl)benzene features six-membered chelate rings, a rarer feature than the usual five-membered chelate rings common to the majority of metal complexes studied to date. The related N^N^N-coordinating ligand, 2,6-di(8-quinolyl)pyridine, has also been used to prepare a complex of the form [Pt(N^N^N)Cl]+, which, unlike [Pt(tpy)Cl]+, displays moderately intense luminescence in solution, attributed to a more favourable bite angle. The corresponding [Ir(N^N^N)2]3+ complex is also reported.

This thesis concerns the synthesis and characterisation of new di(pyrazolyl)pyridine and di(pyrazolyl)pyrazine derivatives, and their iron(II) complexes which exhibit spin crossover behaviour. The examination of their magnetic behaviour using NMR spectroscopy, X-ray crystallography and magnetic measurements is described. Chapter One introduces the background behind the spin crossover phenomenon, especially in the case of iron(H) compounds. The methods of identification and the applications of spin crossover are discussed. Finally the aims of the research are also detailed. Chapters Two and Three discuss the synthesis and characterisation of previously unreported 2,6-di(4-R-pyrazol-I-yl)pyrazine compounds (R ~ CI, Br, I, Me, NO" NH" CCPh). The synthesis of their iron(ll) complexes as BF, and CIO, salts is also detailed, and their magnetic behaviour is discussed and compared to previous 2,6- bis(pyrazol-l-yl)pyridine complexes. The crystal structures of the complexes are presented. Chapter Four is a study of novel di(pyrazol-l-yl)pyridine derivatives substituted at the pyrazolyl or pyridyl 4-positions, and their iron(Il) complexes as before. Magnetochemical data for three complexes are presented, together with crystallographic data and a discussion relating structure to magnetic behaviour. Chapter Five focuses on the study of di(pyrazolyl)pyridine derivatives substituted at the pyridyl 4-positions by azo, ethynyl or styryl groups, and their iron(ll) complexes. Examination of their magnetic behaviour and crystal structures demonstrates the difficulty of predicting the spin state of an iron(lI) complex.

This thesis describes the preparation, structure and activity of a range of binary, ternary and quaternary molybdenum nitrides. It has been shown that all of the samples analysed can be formed through the reaction of the respective molybdate precursor with either ammonia or 3:1 H2/N2 gas mixture. The structures of the nitrides have been studied in detail. These structural findings were then linked to the activity potential of the materials to act as stores of activated nitrogen. The main body of work focused on the ternary molybdenum nitrides of cobalt, iron and nickel with a view to understanding their differences and similarities. Full structural analysis was performed using powder X-ray diffraction (PXRD) and neutron diffraction (PND). The activity of the nitrides was examined by reaction with 3:1 H2/N2 and with 3:1 H2/Ar at various temperatures. Particular attention was paid to the reactivity of lattice nitrogen. The cobalt molybdenum nitride was shown to be special case in this regard where the nitrogen is mobile and relocates within the lattice to a different crystallographic site. This mobility and relocation is concomitant with the loss of 50% of the lattice nitrogen from the system resulting in a phase change from Co3Mo3N to the unprecedented Co6Mo6N phase. The physical and chemical properties of this novel phase have been fully characterised and studied. Interestingly, the isostructual Fe3Mo3N behaves differently and the nitrogen remains fixed and the structure and stoichiometry constant throughout the testing procedure. Further studies of the ternary molybdenum nitrides extended to nickel molybdenum nitride, which was shown to be the least active when tested under both gas mixtures, and analogously to the iron molybdenum nitride the nitrogen is fixed within the β-Mn structured nitride. Further investigations were undertaken, resulting in the successful formation of a series of quaternary nitrides (Fe3-xCoxMo3N). These materials show properties similar to the Co-Mo-N system when the material is cobalt rich and behave similarly to the Fe-Mo-N system when iron rich.

There has been an increase in the interest in fluoride materials over the last decade. This interest has focused on multiferroic materials and kagome lattices, to name but a few areas. This thesis focuses on the synthesis and crystallographic characterisation of selected transition metal fluorides and oxyfluorides. Work is presented on the tetragonal tungsten bronze solid solutions of KₓFeF₃, where x = 0.58 and x ≈ 0.5, and the copper analogue, K₃Cu₃Fe₂F₁₅; the kagome structure of Cs₂ZrCu₃F₁₂; and hydrothermal reactions using vanadium, manganese, or molybdenum as the transition metals in the formation of new fluorides and oxyfluorides. The tetragonal tungsten bronze compounds KₓFeF₃ (x = 0.58 and x ≈ 0.5) are both tetragonal at 500 K. In the variant with the lower K-content, there is a clear phase separation into two tetragonal phases even at this temperature. The K₀.₅₈FeF₃ sample separates into two distinct phases below 340 K to possess one tetragonal and one orthorhombic phase. Then at roughly 300 K, both samples undergo a phase transition where the tetragonal phase in the P4/mbm space group in K₀.₅₈FeF₃ changes to an orthorhombic phase with a larger unit cell; and the tetragonal phase in P4₂bc for the K₀.₅FeF₃ sample changes to the same orthorhombic model, whilst the P4/mbm model remains unchanged. The evolution of the lattice parameters and phase fractions is studied in detail using synchrotron powder X-ray diffraction (sPXRD). The kagome structure investigated, Cs₂ZrCu₃F₁₂, possesses the “ideal” kagome lattice at room temperature, but previous work has suggested that there is a phase transition at 225 K. The two structures are determined by single crystal X-ray diffraction at 300 K and 125 K. Variable temperature sPXRD studies are performed between these two temperature ranges to determine the phase evolution as a function of temperature. The structure changes from a rhombohedral to a monoclinic phase at low temperature. This is the result of the buckling of the kagome layers at the phase transition. The Zr⁴⁺ ion changes from 6 to 7 coordinate and this is seen as the main driving force for the distortion of the kagome layer from its “ideal” planar arrangement. ii The phase transition is first-order as seen from the electrical impedance measurements. The hydrothermal reactions presented reveal seven new materials and their crystal structures. Sr₂V₂F₁₀·H₂O is new and found to be isostructural to Sr₂Fe₂F₁₀·H₂O. BaVO₂F₃ is a cubic material that is potentially piezoelectric. Two hybrid organic inorganic manganese compounds are reported. The ladder structure (C₃N₂H₅)[Mn₂F₆(H₂O)₂] crystallises in a polar space group and shows promise as a candidate for multiferroic studies. The second hybrid material, (C₇NH₁₆)₂[MnF₅(H₂O)]·2H₂O, crystallises in a centrosymmetric space group. The Mo hybrid materials are all centrosymmetric and possess isolated molybdenum-centred monomeric or dimeric octahedral units.

The synthesis and characterisation of a series of novel borane, boryl and borylene complexes of electron rich group 8 and 9 metal centres are described in this thesis. Chapter 3 reports on the properties of a highly nucleophile tolerant borylene system, [CpFe(dmpe)(BNMe₂)]⁺, together with its surprising formation via an unprecedented spontaneous halide ejection process. The incorporation of strongly electron releasing ancillary phosphine ligands is reflected by an Fe-B distance (ca. 1.80 Å) which is more akin to alkyl/aryl substituted borylene complexes, and perhaps more strikingly, by the very low exothermicity associated with the binding of pyridine to the two-coordinate boron centre (∆H = -7.4 kcal mol⁻¹ cf. -40.7 kcal mol⁻¹ for BCl₃). Despite the strong π electron release from the metal fragment implied by this suppressed reactivity and short Fe-B bond, the barrier to rotation about the Fe=B bond in the asymmetric variant [CpFe(dmpe){BN(C₆H₄OMe-4)Me}]⁺ is very small (ca. 2.9 kcal mol⁻¹). This apparent contradiction is rationalised by the orthogonal orientations of the HOMO and HOMO-2 orbitals of the [CpML2]⁺ fragment, which mean that the M-B π interaction does not fall to zero even in the highest energy conformation. The reactivities of the aminoboryl complexes, CpFe(CO)₂B(NR₂)Cl (R = Me, Cy), towards electrophiles (H⁺, Me⁺) are discussed in Chapter 4, with a view to probing potential modification of the boryl ligand substituents. The reaction of CpFe(CO)₂B(NCy₂)Cl with [Me₃O][BF₄] leads to the formation of CpFe(CO)₂B(NCy₂)F. Subsequent reactivity with Brookhart’s acid results in the formation of the known difluoroboryl system CpFe(CO)₂BF₂. Reaction of the dimethylaminoboryl complex CpFe(CO)₂B(NMe₂)Cl with [Me₃O][BF₄] generates CpFe(CO)₂BF₂ directly; however, reaction of CpFe(dmpe)B(NMe₂)Cl with [Me₃O][BF₄] is limited to the formation of CpFe(dmpe)B(NMe₂)F, presumably on steric grounds. Additionally, given the enhanced stability of the bis(phosphine) ligated systems, [CpM(PR₃)₂(BNR2)]⁺ compared to related dicarbonyl ligated complexes, it has also proved possible to synthesise other borylene complexes e.g. [CpFe(dmpe)(BOMes)]⁺ which are otherwise unstable under ambient conditions. Chapter 5 reports the coordination and B-H bond activation of aminoboranes at ruthenium and iridium metal centres. Reaction of aminoboranes, H₂BNR₂, with 14-electron fragments of the type [Cp*RuL]⁺, leads to κ² coordination. The interaction with 16- electron fragments, [CpRu(PR₃)₂]⁺, has also been probed. In contrast to side on-binding of isoelectronic alkene donors, an alternative κ¹-(σ-BH) mode of aminoborane ligation has been established, albeit with binding energies only ~ 8 kcal mol⁻¹ greater than for those for analogous dinitrogen complexes. Variations in ground-state structure and exchange dynamics as a function of the phosphine ancillary ligand set are consistent with chemically significant back-bonding into an orbital of B-H σ* character. By contrast, simple borane coordination compounds prove difficult to isolate on addition of aminoboranes, H₂BNR₂, to in situ generated sources of [(p-cymene)Ru(PR₃)Cl]⁺; spontaneous loss of HCl to generate a rare class of primary hydridoboryl complexes is witnessed instead. Attempts to synthesise boryl complexes via simple oxidative addition of monomeric aminoboranes have also proved successful, through the use of electron rich iridium precursors containing the [Ir(PMe₃)₃] fragment. This step results in the synthesis of novel amino(hydrido)boryl complexes, Ln(H)M{B(H)NR₂}; subsequent conversion (on loss of an ancillary ligand) to a borylene dihydride system proceeds via a novel B-to-M α hydride migration. The latter step is unprecedented for group 13 ligand systems and is remarkable in offering α-substituent migration from a Lewis acidic centre as a route to a two-coordinate ligand system.

This thesis describes the growth, structural characterisation, magnetic and magneto-optics properties of lanthanum strontium manganite (LSMO), GdMnO3 and transition metal (TM)-doped In2O3 thin films grown under different conditions. The SrTiO3 has been chosen as a substrate because its structure is suitable to grow epitaxial LSMO and GdMnO3 films. However, the absorption of SrTiO3 above its band gap at about 3.26 eV is actually a limitation in this study. The LSMO films with 30% Sr, grown on both SrTiO3 and sapphire substrates, exhibit a high Curie temperature (Tc) of 340 K. The magnetic circular dichroism (MCD) intensity follows the magnetisation for LSMO on sapphire; however, the measurements on SrTiO3 were dominated by the birefringence and magneto-optical properties of the substrate. In the GdMnO3 thin films, there are two well-known features in the optical spectrum; the charge transfer transition between Mn d states at 2 eV and the band edge transition from the oxygen p band to d states at about 3 eV; these are observed in the MCD. This has been measured at remanence as well as in a magnetic field. The optical absorption at 3 eV is much stronger than at 2 eV, however, the MCD is considerably stronger at 2 eV. The MCD at 2 eV correlates well with the Mn spin ordering and it is very notable that the same structure appears in this spectrum, as is seen in LaMnO3. The results of the investigations of Co and Fe-doped In2O3 thin films show that TM ions in the films are TM2+ and substituted for In3+. The room temperature ferromagnetism observed in TM-doped In2O3 is due to the polarised electrons in localised donor states associated with oxygen vacancies. The formation of Fe3O4 nanoparticles in some Fe-doped films is due the fact that TM-doped In2O3 thin films are extremely sensitive to the growth method and processing condition. However, the origin of the magnetisation in these films is due to both the Fe-doped host matrix and also to the nanoparticles of Fe3O4

The development of a new class of phosphine-alkene and thio-phosphine-alkene ligands based on a chalcone ferrocene framework, represents the primary focus of this study. The synthesis and characterisation of novel ligands, ferrochalcone 32 and thio-ferrochalcone 33, are described. The related alkene-phosphine ligands, the Lei ligand 17 and novel thio-Lei ligand 46, are further detailed. The coordination chemistry of four ligands (17, 32, 33 and 46) with various transition metals (Pt, Pd, Cu, Rh and Au) has been investigated in a comprehensive spectroscopis study. Single crystal X-ray analysis has been conducted at suitable junctures within the project. A surprising finding was that some solution-state structures were found to be different when studied in the solid state. The AuI complexes-containing the ligands have been successfully used in 1,5-enyne cycloisomerisation reactions. In addition to the coordination chemistry of the novel ligand systems, some interesting findings emerged For example, AuI complex of Lei ligand 17 and monodbaPHOS 74 undergoes an interesting solid-state [2+2] intramolecular cycloaddition transformation, giving cycloadduct, 72 and 77. An interesting finding includes the presence of impurity in commercially available Pd(OAc)2. Cyclopalladation of papaverine was carried out using pure and impure Pd(OAc)2, which resulted in the identification of novel Pd-dimer complex, 86. The result suggest that nitrite contaminants derive from impurities in Pd(OAc)2, and not from the oxidation of acetonitrile mediated by metallic Pd0, explain the formation of PdII-nitrito cyclopalladated products. Photocrystallographic metastable linkage isomerisation and complete conversion to an oxygen-bound nitrito complex 90 was also observed.

Metal fluoride complexes that are extremely sensitive to air and water have been characterized by liquid injection field desorption/ionization (LIFDI) mass spectrometry. Dilute solutions of fluoride complexes of nickel, rhodium, titanium, zirconium, hafnium and ruthenium in toluene and tetrahydrofuran were examined by LIFDI methods on a time-of-flight mass spectrometer. All the spectra of nickel, titanium zirconium and hafnium complexes exhibited the molecular ion as base peak. The ruthenium and rhodium complexes showed loss of HF from the molecular ion as base peaks but the molecular ions were easily detected. Two new nickel fluoride complexes are formed by C-F activation reactions with 2,3,5,6-tetrafluoro-4-dimethylaminopyridine and 2,3,5,6-tetrafluoro-4-methoxypyridine yielding 3,5,6-trifluoro-4-dimethylaminopyridine nickel fluoride and 3,5,6-trifluoro-4-methoxypyridine nickel fluoride, respectively. The crystal structure of 3,5,6-trifluoro-4-dimethylaminopyridine nickel fluoride shows typical square planar coordination at nickel with an Ni-F distance of 1.8521(9) Å. pentamethylcyclopentadienyl metal difluoride (metal = Ti, Zr, Hf) complexes were synthesized from the reaction corresponding metal dichloride with NaF. N,N-dimethylethylene-1,2-diamine metal difluoride complexes (metal = Zn, Co, Ni) were synthesized from the reaction of metal difluoride with N,N-dimethylethylene-1,2-diamine. Ruthenium difluoride complexes were prepared from the reaction of ruthenium bis bifluoride complexes with TMAF. The compounds were characterized by multinuclear NMR spectroscopy and LIFDI mass spectrometry. The nickel monofluoride complexes do not provide useful mass spectra by EI or ESI methods. Only the difluoride complexes of titanium, zirconium, hafnium, ruthenium, zinc, cobalt and nickel species showed evidence of the fluoride ligands in the ESI spectra. Collision induced dissociation (CID) was used to investigate the fragmentation pattern of the ions formed in the ESI mass spectrum. It was observed that the ligand attached to the metal has an effect on the fragmentation pattern of complex and the presence of phosphine strengthens the metal fluoride bond. A modified quadrupole mass spectrometer was used to carry out gas phase ion molecule (I-M) reaction of metal ions with liquid and gaseous neutral molecule. Transition metal fluoride complexes did not show evidence of I-M reactions while Re and Mn tricarbonyl complexes have shown 100% conversion to the product. The decay pathway of multiply charged anions (MCAs) of Ti and Zr was also investigated and it was found that these ions decay through ionic fragmentation rather than electron detachment. Hydrogen bonding of pentamethyl cyclopentadienyl difluoride complexes of Ti and Zr with indole and 1,1,1,3,3,3 hexafluoroisopropanol was studied using fluorine NMR spectroscopy. Change in entropy and change in enthalpy were calculated from the equilibrium constant values (K) using Van’t Hoff’s equation.

An exploration of some organic-inorganic hybrid metal fluorides and lanthanide containing metal organic frameworks (Ln-MOFs) has been carried out under ionothermal conditions. In this synthesis technique an ionic liquid (IL) or deep eutectic mixture (DES) is used as the solvent and in many cases as the provider of the organic structure directing agent. A wide range of ILs and DESs have been investigated as the reaction solvent for the synthesis of organically templated vanadium fluorides and oxyfluorides (VOFs), and initially this has proved to be successful with the isolation of 13 phases, including eight new materials. In the VOFs synthesis the IL acts as a solvent, however the DES acts as a solvent and also as a template delivery agent, where the expected template is provided by the partial breakdown of the urea derivative component. Interestingly, it has been shown that the same structure can be accessible via two different ways; either by using IL with an added templating source, or simply through the use of a DES without any other additive; since the template is provided by the in situ breakdown of the DES. The synthesis of VOFs with extended structures was achieved by the use of the hydrophobic IL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM Tf₂N) as the solvent. [HNC₅H₅][V₂O₂F₅] represents the first VOF with a 2D network that contains exclusively V⁴⁺. This material may be considered as arising via condensation of the previously known ladder-like chains. Furthermore, using imidazole as an added template has produced another layer material that has significant similarities to the [HNC₅H₅][V₂O₂F₅] structure, but with some key differences. Within the same system three other phases were also isolated, including two novel materials displaying the known ladder-type building units. Further investigations in the ionothermal synthesis of VOF using EMIM Tf₂N resulted in a successful synthesis of [NH₄]₂[HNC₇H₁₃][V₇O₆F₁₈], a novel material displaying a unique double layered topology featuring a S = ½ kagome type lattice of V⁴⁺ ions (d¹). Two of the V⁴⁺ based kagome sheets are pillared by V³⁺ ions to form a double layered structure templated by both ammonium and quinuclidinium cations. This compound exhibits a high degree of magnetic frustration, with significant antiferromagnetic interactions but no long range ordering was observed above 2 K. This material presents an interesting comparison to the famous Herbertsmithite, ZnCu₃(OH)₆Cl₂, and may provide an excellent candidate for realising a quantum spin liquid (QSL) ground state. Interestingly, in this system the use of EMIM Tf₂2N as a solvent produces mainly V⁴⁺-containing materials, despite the high reaction temperature (170 °C). This characteristic is unprecedented in VOFs synthesis, as rising the reaction temperature above 150 °C in other techniques (i.e. hydrothermal synthesis) would often result in further reduction of V⁴⁺ to V³⁺. Using the ionothermal technique in the synthesis of hybrid iron fluorides resulted in the isolation of three chain-type materials. Again, the IL acts as the solvent and the DES acts as the solvent and also as the template provider where the expected template is released by the partial breakdown of the urea derivative component of the DES. The synthesis of Ln-MOF using a choline chloride/ 1,3-dimethylurea deep eutectic mixture has produced three novel isostructural materials. Usually, in ionothermally prepared materials (i.e. zeolites) the urea portion of the DES is unstable and breaks down in situ to form ammonium or alkylammonium cations. In the ionothermal synthesis of Ln-MOF, 1,3-dimethyurea (DMU) remains intact and is occluded in the final structure. Using a choline chloride/ethylene glycol deep eutectic solvent led to the isolation of a Ln-MOF with interesting structural properties, however none of the DES components appeared in the final structure. These results demonstrate once more the usefulness and applicability of the ionothermal synthesis method and emphasise how this synthesis technique can be further extended and applied in the preparation of important structures with unique properties and functionalities.

Chapter One gives an overview of molecule-based magnetic materials, and a summary of topics of current interest in this field such as spin crossover (SCO), molecule-based magnets (particularly three room temperature metallo-organic magnets), Metallo-organic frameworks (MOFs), free radical magnets and single molecule magnets (SMMs). There is a brief introduction of key examples and developments in the specific topics, and a perspective at the end. Chapter Two introduces a family of optically pure Fe(II) polymeric chain complexes of formula {FeL2(μ-pz)}∞ and {FeL2(μ-bpy)}∞. [L = bidentate Schiff base ligands obtained from (R)-(+)-α-phenylethanamine and 4-substituted salicylaldehydes]. The structural and magnetic properties of the polymeric products are determined by single crystal X-ray diffraction and SQUID magnetometry. By fitting magnetic data of these complexes with the Bonner- Fisher 1-D chain model, the magnitudes of their magnetic exchanges are rationalised on the basis of substituent electronic properties and bridging ligand identity. Chapter Three describes two Fe(II) coordination polymers containing pyridineconjugated Schiff base isomer ligands. The isomerism of the two ligands leads to a change from trans to cis coordination in the [FeL2] SBU and thus from a tetrahedral diamond-like 3 D network exhibiting a gradual SCO to a 2 D hard magnet. Furthermore, we have also sythesised another four Cu(II) complexes based on these two ligands. Crystallographic studies reveal their structures ranging from 1 D zigzag chains and 2 D mat while their magnetic properties are transformed from ferro- to ferrimagnetic behavior. Chapter Four focuses on three pyrrole-2-ketone bidentate ligands. Three transition metal ions Mn2+, Fe2+ and Co2+ were studied, based on which twelve complexes have been made. The system is structurally diverse, with 1 D, 2 D, monometallic, trimetallic “sandwich” structures and a high nuclearity cluster being observed depending on the use of cations and solvents. Unusual magnetic phenomena are discovered, including a system in which SCO and ferromagnetic coupling are present. Chapter Five details the experimental procedures used to carry out the work in this thesis.

Molybdenum and vanadium inorganic framework materials, with structures based on phosphate and arsenate tetrahedra have been synthesised by hydrothermal techniques and characterised by single crystal X-ray diffraction; additional techniques including thermogravimetric analysis, electron dispersive spectroscopy and infrared spectroscopy were carried out to fully characterise these materials. Of the molybdenum phosphates that have been synthesised, a new layer structure type has been identified. This exhibits perpendicular channels through the molybdenophosphate sheets wherein multiple guest ions, ammonium cations and free orthophosphate (PO4)3- or halide (Cl-, Br-), are hosted. Anion exchange investigations were performed, showing the affinity of the Br- analogue to be completely exchange with Cl- anions. Hydrothermal syntheses with a variety of organic amines resulted in the formation of four compounds. These include three distinct cluster polyanions in addition to a ribbon structure type. The effect of fluoride ions into the synthesis of molybdenum phosphates has been investigated; this approach has led to the discovery of a new oxyfluorinated molybdenum phosphate compound templated by piperazine. Further studies were concentrated on the preparation of molybdenum phosphonate compounds. An amine template bipyridine. During investigations of the role of fluoride ions in the formation of vanadium phosphate and arsenate frameworks, four amine templated compounds have been synthesised and fully characterised. Three of these materials presented, exhibit similar but rather distinct framework topologies including two new layered structure types, which comprise flat or super-corrugated vanadoarsenate layers, and onedimensional tubular structure. Reactions were also performed using inorganic templates, and a number of new structure types were produced with ammonium, rubidium, barium and caesium. The series of materials includes two-dimensional layer structures, and two main structural topologies have been generally observed. During investigations into vanadium borate and phosphate compounds, a threedimensional vanadium phosphate was discovered. Further studies on previously reported vanadium polyborate compounds have led to the isolation of the series of the analogous alkali metal templated structures

Ammonia borane has attracted significant interest in the field of hydrogen storage due to its high gravimetric hydrogen content. In this study the reaction of NH\(_3\)BH\(_3\) with various metal hydrides was investigated. The reactions with hydrides of lithium and sodium required a molar ratio of 1:2 in favour of NH\(_3\)BH\(_3\) and the reaction products were characterised as [Li(NH\(_3\))]\(^+\)[BH\(_3\)NH\(_2\)BH\(_3\)]\(^−\) and [Na]\(^+\)[BH\(_3\)NH\(_2\)BH\(_3\)]\(^−\), respectively, through solid state \(^1\)\(^1\)B and \(^2\)\(^3\)Na MAS NMR and Raman spectroscopy. The reaction of CaH\(_2\) with NH\(_3\)BH\(_3\) required a reaction stoichiometry of 1:4 and this reaction proceeded through a different reaction mechanism, forming Ca(BH\(_4\))\(_2\)•2NH\(_3\). The crystal structures of Ca(BH\(_4\))\(_2\)•2NH\(_3\) and Ca(BH\(_4\))\(_2\)•NH\(_3\) were determined by powder diffraction methods and the reaction pathway investigated through solid state \(^1\)\(^1\)B MAS NMR spectroscopy. The thermal desorption properties of these hydrogen rich materials were investigated and hydrogen was released from all the materials. However, under certain conditions ammonia was the major gaseous desorption product from Ca(BH\(_4\))\(_2\)•2NH\(_3\) and was observed as a minor product from the decomposition of [Li(NH\(_3\))]\(^+\)[BH\(_3\)NH\(_2\)BH\(_3\)]\(^−\). Ammonia was also released during the synthesis of [Na]\(^+\)[BH\(_3\)NH\(_2\)BH\(_3\)]\(^−\), but the decomposition of this material was free from ammonia release. Ramped thermal desorption studies of [Na]\(^+\)[BH\(_3\)NH\(_2\)BH\(_3\)]\(^−\) and [Li(NH\(_3\))]\(^+\)[BH\(_3\)NH\(_2\)BH\(_3\)]\(^−\) to 350°C resulted in weight losses due to hydrogen desorption of 7.5 wt% and 12.5 wt%, respectively. Heating Ca(BH\(_4\))\(_2\)•2NH\(_3\) to 350°C resulted in a total weight loss of 27.5 wt%, which was predominantly due to NH\(_3\) desorption. Powder XRD and solid state \(^1\)\(^1\)B MAS NMR spectroscopy were employed to identify the solid decomposition products and decomposition pathways were proposed. Metal borohydrides were identified in all cases as well as polymeric products possessing B–N chains.

This thesis investigates the structural and physical effects of changing the ratio of Mn:Ga in the anion deficient perovskite, YSr\(_3\)Mn\(_{4-x}\)GaxO\(_{10.5}\). YSr\(_3\)Mn\(_{4-x}\)GaxO\(_{10.5}\) crystallises in the tetragonal space group I4/mmm, with lattice parameters a~7.64 Å and c~15.66 Å. Magnetic characterisation indicates that the material is antiferromagnetic overall, with ferromagnetic ordering in the [001] direction of the unit cell. Earlier work on the structural analogue, Y\(_{1.07}\)Sr\(_{2.93}\)Mn\(_{2.67}\)Ga\(_{1.33}\)O\(_{10.5}\), identified a magnetic peak in the neutron diffraction pattern that could not be fitted following refinement of NPD data. This work concluded that the extra peak was due to a small MnO impurity. The effects of oxidation and fluorination on the structural and physical properties of YSr\(_3\)Mn\(_{4-x}\)Ga\(_x\)O\(_{10.5}\) with various Mn:Ga ratios are investigated. The physical and structural effects of substituting Mn\(^{3+}\) or Co\(^{3+}\) for Fe\(^{3+}\) in the perovskite related material, Pb\(_4\)Fe\(_3\)O\(_8\)Cl, have been investigated using XRPD, NPD and magnetic susceptibility measurements. An earlier characterisation of Pb\(_8\)WO\(_{10}\)Cl\(_2\) suggested a deficit on all atom sites within the unit cell. This work suggests a different structure with an intact cation and main oxygen sub-lattice. The site of an additional oxygen was established linked to tungsten. Pb\(_8\)WO\(_{10}\)Cl\(_2\) crystallises in space group I4/mmm, with a = 3.9846(2) and c = 22.690(2) Å.

The work in this thesis deals with computational studies of manganese ions and atoms in the gas-phase and in the solid phase. The results are divided into three chapters, and the theory and methods used are explained and discussed in a separate theory chapter. The first results on manganese and its coordination to water and methanol molecules in the gas-phase are discussed in the light of physical properties for different ligands including water and methanol. Preferred coordination of a specific ligand type, preferred complex or cluster size as well as coordination modes are thoroughly investigated. Also discussed is stability against proton-transfer reactions for a few manganese-water and manganese-methanol clusters. The work is carried out at the HF/6- 31G(d), MP2/6-311G(d,p) and B3LYP/6-311(3df,3pd)-level of theory using the computer code Gaussian. The results presented here are in good agreement with experimental results and findings. It is concluded that mixing between 4s and 3d orbitals on the manganese atom is responsible for preference for a specific cluster size and that occupation of anti-bonding orbitals destabilizes the cluster, for a specific coordination mode. The next results are for manganese atoms in a double layer of graphite, using the computer code Aimpro. Different coordination modes are investigated as are magnetic properties upon adsorption and modification of the band structure compared to a pristine double layer of graphene. Only one case of a significantly high spin polarization is encountered, and the spin polarization on the manganese atom and the surrounding carbon atoms is investigated with Mulliken analysis. This study is in agreement with previous work in the same field, but provides a more realistic picture since a larger system is considered here. The final chapter deals with manganese atoms in metal-organic frameworks, MOFs, using the Aimpro code. Magnetic properties and binding energies for adsorption of selected molecules are discussed in this chapter. Magnetic properties are discussed using Mulliken analysis. Modification of the band structure upon coordination of these gas molecules is shown and investigated. Very few experimental results exist in this field for this structure, but its role as a potential candidate for hydrogen storage will specifically be discussed.

I. A series of group 14 β-­diketiminate alkoxides (BDI)EOR (BDI = [CH{(CH3)CN-­‐2,6-­‐iPr2C6H3}2; E = Ge, Sn, Pb; R = iPr, sBu, tBu) was synthesised and characterised. The reactivity towards aliphatic and unsaturated electrophiles was investigated. For the tin and lead systems, an unexpected trend was observed. For instance, they do not or very sluggishly react with aliphatic electrophiles, but readily activate carbon dioxide. The slower tin system was used to investigate the mechanism of carbon dioxide insertion through detailed kinetic, thermodynamic and DFT studies. The isostructural germanium system showed a different reactivity pattern. Treatment with aliphatic electrophiles and iodine leads to cationic Ge(IV) oxidative addition products, whereas reactivity towards heterocumulenes was not observed. The Lewis basic behaviour was also investigated, revealing that the germanium lone pair coordinates to copper(I) iodide. The synthesis of an isostructural mercury system was also attempted, resulting in the formation of the first homoleptic bis­‐β­‐diketiminate complex bound through the γ­‐carbons. II. Monosubstituted paracyclophane was exploited in the synthesis of a novel β­‐diketimine and enaminone both possessing planar chirality. These were used to stabilise N,N'- and N,O-­chelated scandium and zirconium complexes, potentially suitable for asymmetric hydroamination catalysis. Preliminary tests show nocatalytic activity.

Chapter One presents an overview of olefin polymerisation, which provides the context for the majority of the work described in later chapters. Both Ziegler-Natta and late transition metal systems are described. Chapter Two describes the synthesis and reactivity of trisamido titanium complexes with the diarylamido fragments derived from diphenylamine and di-p-tolylamine. These complexes have been thoroughly studied using NMR spectroscopy. This chapter also presents the syntheses of two rare examples of trisamido methyl complexes. In addition, an improved synthetic route to the cocatalyst, KB(C6F5)4 and the structures of [B(C6F5)3·C4H8O] and [Mg(C6F5)2(Et2O)(dioxane)] are described. Chapter Three describes the polymerisation activity of the catalysts derived from (R2N)3TiCl, (R2N)3TiMe, and [(R2N)3Ti]+ with the cocatalysts MAO, B(C6F5)3, and KB(C6F5)4. Data was recorded for each of the catalysts, and the consumption of propene over time was plotted. Rate constants were found for each of the polymerisation reactions. The mechanism for the polymerisation of each of these was also examined. Chapter Four presents the synthesis and reactivities of new trisamido complexes using 10,11-dihydro-dibenz(b,f )azepinyl, hereafter abbrievated as dda, as the amide fragment. Specifically, syntheses of (dda)3TiCl, (dda)3TiMe and (dda)3TiBH4 are described and their characterisation by NMR spectroscopy and X-ray crystallography is presented. The use of these complexes in synthetic approaches to (dda)3TiH are described. Initial steps in the characterisation of hydride transfer to CO2 from (dda)3TiH are also presented. Chapter Five presents details for the experimental work and Appendices are included, containing selected experimental data.

Chapter 1 gives a brief review of oxychalcogenide materials and their properties, particularly those with structures similar to systems discussed in the later chapters. Particular attention is paid to the structural and magnetic properties of La2O2Fe2OSe2-type materials, work on which is presented in chapters 3–5. These oxychalcogenides, along with ZrCuSiAs-related materials, are of interest due to their potentially interesting magnetic and conducting properties. In particular they are close relatives of the LaOFeAs superconductors. Chapter 2 describes the synthetic and analytical techniques used in this project. The theory behind the powder diffraction techniques used throughout is described, and information on specific methodology used in the data collections and analysis of this work is given. SQUID magnetometry is also discussed. Chapter 3 discusses the variable temperature structural and magnetic properties of La2O2Mn2OSe2 and Pr2O2Mn2OSe2, as well as those of the newly prepared material Ce2O2Mn2OSe2. These materials are observed to undergo a phase transition on cooling revealed by a change in the thermal expansion of the c cell parameter, and show evidence for the static disorder of oxide ions from the [Mn2O]2+ plane below this temperature. Pr2O2Mn2OSe2 is also shown to undergo a further transition on cooling below 36 K to an orthorhombic unit cell. Neutron diffraction data have also shown that the Mn2+ moments in these materials order with an AFM1 structure on cooling below ~180 K. Chapter 4 describes the study of both La2O2Fe2OS2 and La2O2Fe2OSe2 by variable temperature neutron powder diffraction. These materials have been demonstrated to order with an AFM3 structure on cooling below ~100 K, which is coincident with a subtle structural change observed in the thermal expansion of the a cell parameter. The unexpected adoption of the AFM3 magnetic structure is discussed in relation to structurally similar iron-based superconductors. Chapter 5 presents the synthesis of several new La2O2Fe2OSe2-type materials, and the magnetic structure of La2O2Co2OSe2. The stability range over which these materials form is discussed with respect to the size of the metal ions present. A comparison of the structural properties of all the A2O2M2OSe2 materials is given and the various magnetic structures they adopt discussed. Chapter 6 reports the synthesis of a new family of transition metal oxychalcogenides (β La2O2MnSe2). Their structure has been solved from laboratory X ray diffraction data, using a combination of charge-flipping and direct methods, and confirmed by neutron diffraction. Variable temperature structural properties are discussed and show these materials undergo a phase transition on cooling associated with ordering of transition metal ions. SQUID magnetometry and neutron powder diffraction have both demonstrated these materials order antiferromagnetically at low temperatures. Chapter 7 describes the synthesis of two new ZrCuSiAs-related transition metal containing oxychalcogenides: Ce2O2FeSe2 and La2O2ZnSe2. The structure solution of Ce2O2FeSe2 by charge-flipping is reported, alongside the determination of the magnetic structure from neutron powder diffraction data collected at 12 K. The variable temperature structural properties of La2O2ZnSe2 are also reported.

Introduction and Literature Review: Different families of oxide ion conductors and their applications are discussed. Experimental and Characterisation Methods: The synthetic methods and characterisation techniques used throughout this thesis are described. Synthesis, Structure and Transport Properties of Bi2Zr2-xTixO7 Phases: The characterisation of Bi2Zr2-xTixO7 compounds is reported for the first time. An increase in conductivity of 3 orders of magnitude is found for the Zr- rich end member. Bi2Ti2O7, which adopts centrosymmetric space group Fd-3m has been found to be SHG active. Structure Solution of beta-Bi2Sn2O7 and Properties of Bi2Sn2O7 Based Materials: Analysis of synchrotron powder X-ray and powder neutron diffraction data has shown for the first time that beta-Bi2Sn2O7 is not cubic and has a monoclinic structure, most likely in space group Pc. The effect of doping in both Bi2Sn2O7 and Bi2ScNbO7 on their respective conductivities has been explored. Synthesis and Characterisation of Nd2Zr2O7: A range of average and local structural techniques have been used to demonstrate that Nd2Zr2O7 prepared by wet-chemistry routes adopts the fluorite-type structure, as opposed to the pyrochlore structure adopted by samples synthesised by solid state methods. Synthesis, Characterisation, Simulations and Properties of Bi6WO12 and Related Oxide Ion Conductors: We report for the first time details of DFT molecular dynamics simulations to probe the oxide ion conduction pathways in the oxide ion conductor Bi6WO12. Appropriate doping has led to enhancements in oxide ion conductivity. Simulations, Characterisation and Properties of New Bismuth Vanadate Oxide Ion Conductors: DFT molecular dynamics simulations carried out on Bi19V2O33.5 have revealed the O2- migration pathways in this material with exceptional ionic conductivity. The synthesis and characterisation of new doped bismuth vanadates with formula Bi19-xMxV2O33.5-x/2 (M = Ca2+ or Sr2+), also excellent oxide ion conductors, is reported. Overall Conclusions and Suggestions for Future Work: This briefly reviews the conclusions and makes suggestions for further work.

A range of luminescent Ir(III) complexes [Ir(C^N)2(X^Y)]n+ (n = 0, 1) containing different cyclometallated (C^N) and ancillary (X^Y) ligands has been synthesised. All new compounds were fully characterised by 1H and 13C NMR spectroscopy, mass spectrometry and elemental analyses and several compounds have been structurally characterised by X-ray crystallography. The photophysical and electrochemical properties of the complexes were also studied. Chapter one provides an introduction to luminescent transition metal complexes, in particular Ru(II) and Ir(III) complexes and gives an overview of the factors controlling the emission wavelengths of cyclometallated Ir(III) complexes and their applications, particularly as biological labels and probes. Chapter two discusses the synthesis and properties of [Ir(C^N)2(bipy)]+ and shows that substituents para to the metal on the cyclometallated phenyl have a significant effect on the emission wavelength. Chapter three describes complexes [Ir(C^N)2(X^Y)]n+ (n = 1, X^Y = pyridine imine; n = 0, X^Y = pyrrolylimine) and the effect of substituents on the redox properties and emission wavelength. Some of these complexes have been employed in live-cell imaging. In Chapter four the synthesis, characterisation and application of [Ir(C^N)2(phencat-OH)]+ complexes as molybdate sensors is discussed. Chapter five describes the synthesis of [Ir(C^N)2(X^Y)]n+ (n = 0, 1) containing a homochiral X^Y ligand i.e. (S)-soxH, (S)-pepH, (S)-phglyH, (+)-tfacH and (S)-ppea. The complexes are all formed as 1:1 mixtures of diastereomers with Δ or Λ chirality at the metal. Diastereomers containing the (S)-sox and (S)-pep ligands can often be separated via crystallisation or column chromatography. Treatment of a single diastereomer (ΛS or ΔS) with an appropriate acid removes the sox or pep ligand hence provides a route to complexes with only metal-centred chirality, for example Λ- and Δ-[Ir(ppz)2(bipy)]+.

Within this work the effects of metal identity are investigated on the magnetic properties of a range of materials, in which different transition metals are shown to produce significantly different calculated magnetic coupling values when incorporated into the same structure. The model structures composed of transition metals mediated by hydrogen halide ligands of the form FHF-, ClHCl- and FHCl- enable the calculation of magnetic coupling values via hydrogen bonds (HBs), providing insight into a scarcely studied topic. The employment of the well known HF=35% functional, provides results anticipated to represent potential experimental trends. Interesting results are also reported which indicate a relationship between the binding energy of the atom and the level of coupling displayed. The quantum nature of the H atom, often difficult to localise, are also accounted for by use of a shooting algorithm in order to solve the one dimensional Schrödinger equation in relation to the hydrogen positions within the isotropic lattice. Hydrogen positions were fixed during geometry optimisations in order to obtain the E(x) potential energy curve required to allow this to be achieved. Both the in which proton motion is incorporated and J coupling values from the optimised ground state structures, in which the atomic positions including the H positions underwent a full geometry optimisation, are presented. The electronic effects of incorporating different group one and group two metals into the related Prussian Blue (PB), Prussian Yellow (PY) and Prussian White (PW) model lattices are also presented. More specifically band gaps within these complexes are calculated from projected density of state (DOS) plots of the electrons within the atomic orbitals from a converged calculation in which the B3LYP functional (HF=20%) is employed. This functional has previously been shown to provide band gap energies in good agreement with experimental values. The results obtained confirm that the value of ~3eV, associated with an absorption in the yellow region, lies within the PY band gap range, indicated by the HOMO and LUMO orbitals within the DOS plot. Band gaps calculated directly from SCF energy differences do not agree well with experimental values or trends for the various group one PB complexes. A number of related metal containing bromanilic acid (BA) and chloranilic acid (CA) complexes are synthesised, crystallised and their structures, as determined by X-ray single crystal diffraction, reported. The structural packing of the molecules is analysed by defining a number or recurring unit within the structures in order to obtain key similarities. The structures are also broken down in to lower dimensional units composed of the individual components within the asymmetric unit and built up into higher dimensional units such as clusters, chains and planes that all intersect with one another in order to produce the overall three dimensional structures. In most cases the point of intersection is on a key symmetry element such as an inversion centre. Particularly short M-M contact distances are observed in a number of the complexes. This proves interesting within the related isomorphous complexes in which the main effect of incorporating a larger metal cation into the same structure is in the ionic repulsions between the metals. This is particularly interesting in more extended structures in which the metals exist in chains or planes that run along a particular direction of the unit cell. The specific increase in cell parameter can in most cases be explained as a consequence of the repulsion between the shortest M-M contacts. The effect is also observed in structures in which the metals exist as isolated clusters, and also displays some interesting consequential effects on other interactions. A variable pressure neutron single crystal diffraction experiment on a short asymmetric HB is also reported, in which one lattice is compressed significantly more than the other two, an effect that is explained by the change in contact distances with pressure.

Currently, there is interest in the development of molecular-scale devices for use in quantum information processing (QIP). With this application in mind, physical studies on antiferromagnetically coupled molecular wheels [Cr7MF3(Etglu)(O2CtBu)15(phpy)], where M is a divalent metal cation (M = Mn2+, Zn2+, Ni2+) have been pursued. The heterometallic wheels contain an octagon of metal centres, which are bridged by fluoride ions, pivalate groups and a chiral N-ethyl-D-glutamine molecule which is penta-deprotonated and bound to the metal sites through all available O-donors. They are deep purple in colour and they have been named purple-Cr7M. There is antiferromagnetic coupling between adjacent metal centres, J » -8 cm-1, resulting in a non-zero net spin ground state. The spin-Hamiltonian parameters of this family have been determined.At the heterometal site of purple-Cr7M wheels there is a terminal ligand which can be substituted for a variety of N-donor organic ligands. A series of bidentate N-donor linkers has been used to link Cr7Ni wheels (each wheel Seff = 1/2) to create prototype two-qubit systems. Multi-frequency EPR spectroscopy and SQUID magnetometry has been used to extract the spin-Hamiltonian parameters of this family. It has been shown that the single wheels can be linked together electronically as well as chemically. It has been found that for the unsaturated linkers, there is a weaker interaction between Cr7Ni wheels when longer linkers are used. The strength of interaction is smaller for the saturated linkers than for the unsaturated linkers.The formation of 'green'-Cr7M wheels is different, being templated around a cation. Two new types of wheels have been studied: [tBuCONHC6H12NH2C6H12NHCOtBu][Cr7M2+F8(O2CtBu)16] and [Cs?Cr7MF8(O2CtBu)16]·0.5MeCN (where, M = Mn2+, Zn2+, Ni2+), where the former is templated around a long dialkylammonium group and the latter around a caesium cation. The effect of the templating cation on spectroscopic properties has been determined.Physical studies on a family of antiferromagnetically-coupled homometallic clusters have been pursued. They consist of cyclic arrays of homometallic Cr3+ ions in either a octametallic wheel or hexametallic horseshoes. The horseshoes have the general formula: [CrxFx+5L2x-2]n3- (where L = carboxylate). Cr3+ centres are bridged by pivalate groups and fluorides, while Cr3+ centres at the ends of the chain have terminal fluorides completing their coordination sphere. These terminal fluoride groups are labile enough to be substituted, e.g. [EtNH2][Cr6F7(O2CtBu)10(acac)2] is the product of a substitution reaction with acetylacetone.

Metal chalcogenides (sulfides, selenides and tellurides) are materials of current interest due to their peculiar properties such as optoelectronic, magnetooptic, thermoelectric and piezoelectric displays. These semiconducting materials have potential applications in solar cell devices, infrared detectors and ambient thermoelectric generators. Previously, these materials have been deposited by multiple-source precursor route with several problems associated with this technique. This work describes the synthesis of metal complexes (Zn, Cd, Fe, Ni, Pd, Pt) using the imidodichalcogenodiphosphinate ligand (Woollins ligand). Their thermal decomposition together with structural and spectroscopy analysis was carried out. The complexes were used as single source precursors for the deposition of cadmium selenide, cadmium phosphide, cadmium sulfide, zinc selenide, iron selenide and the tellurides of nickel, palladium, platinum and iron as thin films and powders. These were deposited by AACVD and pyrolysis. The deposited thin films and powders were characterised by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), X-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID). The cadmium complexes [Cd{iPr2P(Se)NP(Se)iPr2}2] and [Cd{iPr2P(S)NP(Se)iPr2}2] deposited the mixture of hexagonal CdSe and monoclinic Cd2P3 films at the flow rate of 160 sccm at 475 and 500 °C. At the flow rate of 240 sccm, only hexagonal CdSe was deposited from [Cd{iPr2P(Se)NP(Se)iPr2}2] at all temperatures. Hexagonal CdS and the mixture of orthorhombic Cd6P7/cubic Cd7P10 were deposited from [Cd{iPr2P(S)NP(S)iPr2}2]. The zinc complexes [Zn{iPr2P(Se)NP(Se)iPr2}2] and [Zn{iPr2P(S)NP(Se)iPr2}2] both deposited cubic ZnSe at all temperatures with the flow rates of 160 and 240 sccm. The iron complexes [Fe{(SePPh2)2N}2] and [Fe{(SePPh2NPPh2S)2N}2] deposited orthorhombic FeSe2 mixed with monoclinic Fe3Se4 by pyrolysis at 500 and 550 °C. An unresolved pattern was observed from the complex [Fe{(SePPh2NPPh2S)2N}2] at 550 °C. XPS analysis of the deposited FeSe2 showed the surface oxidation of the material, while the magnetic measurements on the sample using SQUID confirmed its ferromagnetic properties. The telluride complexes of nickel, palladium, platinum and iron deposited the metal telluride respectively as: hexagonal NiTe, hexagonal PdTe, hexagonal PtTe2 (mixed with rhombohedral PtTe) and hexagonal FeTe2. Conductivity studies on NiTe and PdTe revealed them to be insulators, while the magnetic measurements on FeTe2 indicated its antiferromagnetic behaviour.

The synthesis and characterisation of a series of {AnO₂}ⁿ⁺ complexes containing multidentate ligand environments is reported. Three novel {UO₂}²⁺ complexes (1-3) containing N₃O₂ linear pentadentate ligands have been prepared and crystallographically characterised. NMR spectroscopy has been able to show that 1-3 are stable with respect to ligand exchange, in a range of solvents. The strength of the O=U=O unit has been probed by vibrational spectroscopy and 1-3 exhibit some of the weakest O=U=O ν₁ stretching modes reported (802-805 cm⁻¹). The cyclic voltammetry (CV) of 1-3 in various solvents (0.1 M [Bu₄N][PF₆]) has been performed and indicate the position and reversibility of the {UO₂}²⁺/{UO₂}⁺ redox couple has been found to be subtly dependent on the solvation environment. {UO₂}²⁺ complexes (4-6) have been prepared by subtle modification of reaction conditions using a rigid N₂O₂S linear pentadentate ligand. Characterisation by X-Ray diffraction reveals different monometallic systems, where 4 and 5 are solely bound to the O₂ donors of the ligand and 6 exhibits uranyl binding through all of the donor atoms in the N₂O₂S cavity. ¹H NMR spectroscopy shows 5 exhibits intramolecular rearrangement on the NMR timescale in DCM, but undergoes intermolecular ligand exchange in more coordinating solvents (DMSO, py). Cyclic voltammetry of 5 in DCM (0.1 M [Bu₄N][PF₆]) also indicates that rearrangements and/or ligand exchange processes may occur at rate comparable to that of the CV studies. Complex 6 exhibits stability with respect to ligand exchange or rearrangement in various solvents and shows comparable solvation environment dependency of the {UO₂}²⁺/{UO₂}⁺ redox couple, relative to 1-3. Three monometallic {UO₂}²⁺ complexes (7-9) have been prepared using a rigid tetradentate N₂O₂ ligand. A dimetallic {UO₂}²⁺ complex (10) where two {UO₂}²⁺ are linked by a 4,4'-bipyridine bridge, has been formed by controlled ligand exchange. Vibrational spectroscopy shows the presence of the O=U=O ν₁ stretch in both the Raman and infrared spectra for 7-10, likely to be caused by distortion of the ligand about the UO₂}²⁺ equatorial plane causing a change in dipole for the O=U=O ν₁ stretching mode. A synthetic and spectroscopic study of neptunyl coordination to N₃O₂ linear pentadentate ligands has been made. Adopting a similar method that was successfully employed in the synthesis of 1-3, resulted in the reduction of {NpO₂}²⁺ to {NpO₂}⁺, giving a series of complexes (11-13). Complex 13 has been crystallographically characterised and shows a monometallic {NpO₂}⁺ complex which is bound to all of the atoms in the N₃O₂ cavity.

The work presented in this thesis reports the use of a series of novel thiobiuret metal complexes [M(SON(CNiPr2)2)n] (M = Cu, Ni, Fe, Zn, Cd or In; n = 2 or 3) for the first time as single source precursors for the colloidal synthesis of metal sulfide nanoparticles. Other single source precursor(s) were also used for the synthesis of CdSe, CdS, CdSe/CdS core/shell, CdSeS alloys and Cu2-xS nanoparticles in microfluidic reactors. Thermolysis experiments of [Cu(SON(CNiPr2)2)2] using only oleylamine produced Cu7S4 nanoparticles as a mixture of monoclinic and orthorhombic phases. Pure orthorhombic Cu7S4 nanoparticles were obtained when a solution of precursor in octadecene was injected into hot oleylamine whereas, Cu1.94S nanoparticles were obtained when a solution of the precursor in oleylamine was injected into hot dodecanethiol. The thermolysis of [Ni(SON(CNiPr2)2)2] gave Ni3S4 in all cases except when precursor solution in oleylamine was injected into hot octadecene which produced NiS nanoparticles. The thermolysis of [Fe(SON(CNiPr2)2)3] in oleylamine/oleylamine produced Fe7S8 nanoparticles but other combinations, in most cases, gave amorphous material. Thermolysis of [Zn(SON(CNiPr2)2)2] in oleylamine produced spherical ZnS nanoparticles. Particles with size smaller than 4.3 nm had a cubic phase, whereas the particles with size larger than 4.3 nm had a hexagonal crystal structure as suggested by the selected area electron diffraction. Powder X-Ray diffraction showed that the CdS nanoparticles obtained from the thermolysis of [Cd(SON(CNiPr2)2)2] in oleylamine were cubic under all reaction conditions except when dodecanethiol was used as an injection solvent which produced hexagonal CdS. β-In2S3 were synthesized from the thermolysis of [In(SON(CNiPr2)2)3]. Transmission electron microscopy showed that the copper, nickel and iron sulfide nanoparticles had various morphologies such as spherical, hexagonal disks, trigonal disks, rods or wires; depending on the reaction temperature, concentration of the precursor, the growth time and the solvent/capping agent combination. The zinc and cadmium sulfide nanoparticles were mostly spherical whereas the indium sulfide nanoparticles were produced in the form of ultra-thin (< 1.0 nm) nanorods or nanowires. ZnxCd1-xS and CuInS2 nanoparticles were synthesised from the 1,1,5,5-tetra-iso-propyl-4-thiobiureto complexes of Zn, Cd and Cu, In, respectively. Powder X-Ray diffraction showed that the obtained ZnxCd1-xS nanoparticles are cubic under all reaction conditions. The ZnxCd1-xS nanoparticles had an average diameter between 3.5 to 6.4 nm as shown by transmission electron microscopy. The optical properties of the ZnxCd1-xS nanoparticles were highly dependent on the ZnS to CdS precursor ratio and the solvents/capping agents. Chalcopyrite (tetragonal), wurtzite (hexagonal) or a mixture of both CuInS2 nanoparticles were obtained depending on the reaction conditions. TEM showed that the CuInS2 nanoparticles could be synthesised with different morphologies (spherical, hexagonal, trigonal or cone). Luminescent CuInS2 nanoparticles were obtained only in the absence of oleylamine. [Cd(S2CNMenHex)2], [Cd(Se2P(iPr)2)2] and [Cu(SON(CNiPr2)2)2] were used as single source precursor(s) for the synthesis of CdS, CdSe, CdSe/CdS core/shell, CdSeS alloys and Cu2-xS in microfludic reactor. The CdS nanoparticles were in size range of 5.0 to 8.0 nm whereas the CdSe nanoparticles were ultra small (ca. 2 nm) with blue luminescence. The CdSe/CdS core/shell and the CdSeS alloys were bluish green or green luminescent depending on their size. The copper sulfide nanoparticles were found to be monoclinic Cu7S4 or monoclinic Cu7S4 with minor impurities of rhombohedral Cu9S5 depending on the reaction conditions.

A series of compounds with the general formula R3PX2 and R3PX4 (where R = o-tolyl, m-tolyl, p-tolyl, o-anisyl, m-anisyl, p-anisyl, o-thioanisyl, p-thioanisyl, p-fluorophenyl, p-chlorophenyl, mesityl and X = Cl, Br, I) have been synthesised and studied by X-ray crystallography, multinuclear NMR spectroscopy and Raman spectroscopy. A study of the conformational features of the aryl groups in these structures was undertaken in order to investigate the role of steric effects and crystal packing on P-X and X-X bond lengths. Compounds with the general formula RSeX / RSeX3 (where R = p-fluorophenyl, p-chlorophenyl, p-bromophenyl, p-iodophenyl and X = Cl, Br, I) have been synthesised by reacting the diselenides with halogens in the stoichiometric ratios. The X-ray crystal structure of p-ClC₆H₄SeI.I₂ is the first crystallographically characterised example of a compound of stoichiometry RSeI₃, although it is better represented as an I₂ adduct of a Se(II) iodide than a Se(IV) compound. In contrast, (p-FC₆H₄)Se-Se(I)₂(p-FC₆H₄) is an I₂ adduct where the Se-Se bond has not been cleaved by iodine. Both structures are stabilised by weak Se...I and I...I interactions. p-FC₆H₄SeCl₃ is an example of a dimeric structure with bridging chlorines. [Ph₄PX] and Ph₃PX₂ were reacted with PhEX (where E = Se, Te and X = I, Br, Cl) to produce salts containing [PhEX₂]- and [PhEX₄] anions. Where possible all the products were then analysed via NMR and Raman spectroscopy and X-ray crystallography. The reactions of the ligand tris-p-fluorophenyl phosphine with sulfur and selenium are presented along with the subsequent reactions of these compounds with diiodine. All of the compounds are characterised via X-ray crystallography.

A series of cationic Rh(I) diphosphine and phosphine-alkene complexes have been isolated and fully characterised. The reactivity of these species towards hydrogenation, dehydrogenation and dehydrocoupling reactions has been investigated. The use of potentially hemilabile ligands DPEphos and XANTphos in the intramolecular dehydrogenation chemistry of tricyclopentylphosphine is reported. The comparison in reactivity of these isolated diphosphine phosphine-alkene complexes towards hydrogenation and with acetonitrile is discussed along with their ability to dehydrocouple secondary silane, Ph₂SiH₂, and amine-borane H₃B·NMe₂H. The acceptorless dehydrogenation of a tethered cyclopentane with cationic Rh(I) diphosphine complexes has also been extended to include thioethers. Isolated cationic Rh(I) phosphine-alkene complexes with labile fluorobenzene ligands are found to act as a source of the reactive 12-electron [Rh{PR₂(ƞ²-C₅H₇)}]+ (R = cyclopentyl (Cyp)/ iPr) fragment in solution and can coordinate two amine-borane ligands (either H₃B·NMe₃, H₃B·NMe₂H or H₃B·NMeH₂) in a novel and unique bis-σ-binding mode. The catalytic activity of some of these isolated complexes in the dehydrocoupling of H₃B·NMe₂H and H₃B·NMeH₂ has been determined. With a view to further understanding the mechanism of catalytic transition metal assisted amine-borane dehydrogenation and dehydrocoupling, known B-N intermediates H₃B·NMe₂BH₂·NMe₂H and [H₂B·NMeH]₃ were also coordinated to the [Rh{PCyp₂(ƞ²-C₅H₇)}]+ fragment and investigated with regard to their role in the catalytic cycle. Structure activity relationships determined from stoichiometric reactions of cationic Rh(I) diphosphine fluorobenzene complexes with amine-boranes enabled the design of a highly efficient homogeneous catalyst capable of dehydrogenating H₃B·NMe₂H to [H₂BNMe₂]₂ at 0.2 mol% loading in 30 minutes at 298 K. Rapid dehydrogenation and dehydrocoupling of H₃B·NMeH₂ to form high molecular weight poly(N-methylaminoborane) with a low PDI has also been achieved. Investigations using model aminoborane H₂B=NiPr₂ and intermediate B-N species H₃B·NMe₂BH₂·NMe₂H and [H₂B·NMeH]₃ has helped establish an overall mechanistic rationale for this process.

This work focuses principally on two compounds, CeCu1-xOS and LiFeAs, which have related layered structures but exhibit radically different physical properties. The nature of the air sensitivity of the ZrCuSiAs-type oxysulfide CeCu1-xOS has been investigated by neutron diffraction and magnetometry. It was found that this compound can be made fully stoichiometric, with structural and magnetic properties that are consistent with other LnCuOS compounds, indicating that this is a bona-fide Ce3+ compound. Upon air exposure, Cu ions are extruded from the sulfide layer to leave a Cu-deficient phase with contracted unit cell parameters and a diminished paramagnetic moment consistent with mixed-valence Ce3+/4+.The extruded Cu forms CuO and can be re-inserted into the sulfide layer by heating under a reducing atmosphere. This explains the anomalous behaviour of CeCuOS reported throughout the literature and has implications for the behaviour of other layered Cu-sulfides with oxidisable cations. At low temperatures Cu-deficient CeCu0.8OS was found to exhibit structural ordering of Cu+ ions and vacancies, resulting in a √5a x √5a basal expansion of the high-temperature unit cell. The layered iron arsenide LiFeAs was synthesised and found to be superconducting below 17 K. Joint XRD/NPD measurements showed unambiguously that the compound adopts the anti-PbFCl structure with Li ions in a square-pyramidal LiAs5 environment. No evidence was found for an orthorhombic structural distortion at low temperatures. Further diffraction experiments showed that the compound can be made with non-stoichiometric compositions Li1-yFe1-y for small values of y (<0.05), as Fe can be accommodated on the Li site. This type of non-stoichiometry was found to strongly inhibit superconductivity (which was quenched entirely when y>0.02). Three series of compounds of type LiFe1-xMxAs (M = Mn, Co, Ni) were synthesised and characterised struturally bu high-resolution XRD and/or NPD. Substitution by Co and Ni was found to cause a monotonic decrease in Tc, and Ni was found to be twice as effective at suppressing Tc as Co. MuSR measurements showed the penetration depth increasing with Co and Ni substitution, consisitent with the superconducting state becoming less robust. Substitution by Mn was found to strongly inhibit superconductivity, and this behaviour is reminiscent of the non-stoichiometric Li1-yFe1-yAs materials. The structures and superconducting properties of LiFeAs and NaFeAs were studied under high pressures. Equations of state were obtained for each compound. Hydrostatic pressure was found to distort of the FeAs4 away from ideal tetrahedral geometry in both compounds. These changes caused a monotonic decrease in Tc in LiFeAs, but has a smaller and more complex effect on the Tc of NaFeAs. Furthermore, NaFeAs was found to undergo a structural transition above P = 22 GPa, but the high-pressure structure could not be solved and this will become a target for future work.

This Thesis describes the synthesis and characterisation of new Main Group and Rare Earth alkyl, amide, alkoxide and borohydride complexes and their use as catalysts for the ring-opening polymerisation (ROP) of ε-caprolactone and rac-lactide. Chapter 1 introduces ROP from an industrial and academic perspective, as well as polymer characterisation techniques. A literature review is given, with an emphasis placed on Main Group catalysts. Chapter 2 describes the synthesis and characterisation of new homo- and hetero-scorpionate Main Group complexes. An introduction to homo- and hetero-scorpionate ligands is given, as well as a discussion of the ε-caprolactone and rac-lactide ROP activity displayed by the new complexes. Chapter 3 describes the synthesis and characterisation of new neutral and cationic Main Group borohydride complexes supported by the tris(pyrazolyl)methane and tris(pyrazolyl)hydroborate ligands. A review of borohydride complexes is also given. The ε-caprolactone and rac-lactide ROP activity shown by the complexes presented is also discussed. Chapter 4 describes the synthesis and characterisation of new mono- and di-cationic yttrium complexes supported by the tris(pyrazolyl)methane and triazacyclononane ligands. An introduction to the synthesis of neutral and cationic Rare Earth complexes is given. An overview of immortal ROP is also provided. The activity of the new complexes towards the immortal ROP of rac-lactide is also discussed. Chapter 5 contains experimental details and characterising data for the new complexes reported in this thesis. CD Appendix contains .cif files for all of the new crystallographically characterised complexes.

A range of spectroscopic and computational techniques have been applied to the study of three metal cluster systems: vanadium monoxide, the Au2 molecule, and RhnN2O+ clusters. A new instrument has been built for spectroscopy experiments on metal clusters, consisting of a laser ablation cluster source and a linear time-of-flight mass spectrometer. The instrument was characterised using nitric oxide spectroscopy and applied to the electronic REMPI spectrum of vanadium oxide in the visible region. The rotational constants and band origins of several known states have been determined, and the observation of a new spin-forbidden transition has been used to connect the energies of the quartet and doublet manifolds of VO. A new 3 2Π state was also observed and characterised. The photoionisation and photodissociation of Au2 were then studied at 157 nm, and between 35500 and 37200 cm-1 with another new instrument recently constructed in the group. Excited and ground state Au photofragments were produced in both spectral regions, and have been detected and assigned using velocity map imaging. The 157 nm photodissociation produced gold atom products in the seven highest-energy accessible channels in a single-photon dissociation process. The complex near-UV spectrum involved two-photon excitation to two 0g+ excited states close to their dissociation thresholds, followed by predissociation to thirteen different Au product channels. The branching ratios for dissociation into each of these channels varied across the spectrum as different dissociation limits and curve crossings occurred. The mid- and far-infrared multiple-photon dissociation spectra of RhnN2O+ clusters have been recorded using the argon-tagging action spectroscopy technique and free electron laser radiation. The results have been compared to density functional theory calculations to deduce the nature of the binding and the likely low-lying electronic and geometrical structures. The N2O was found to be molecularly adsorbed on the surface of the cluster but, upon infrared heating of the complex via the N2O vibrational modes, was observed to undergo a reaction, producing N2 and cluster oxides RhnO+. The reaction is believed to be thermal and mode-independent, but the efficiency of the surface reaction does vary with cluster size, with the n=5 cluster showing no detectable reaction.

The synthesis and characterisation of a new class of multidentate conformationally flexible phosphino-alkene ligands, called dbaPHOS (127) and monodbaPHOS (128), are described is this PhD thesis. The related phosphine sulphide ligands, namely dbaTHIOPHOS (137) and monodbaTHIOPHOS (149), have also been prepared. The coordination chemistry of the novel ligands was investigated with a variety of late-transition metals, including Cu, Rh, Pd and Pt. X-ray crystal structure determination of the complexes containing these ligands highlights the multiple coordination modes and versatility of each ligand system. The ability of the 1,4-dien-3-one backbone to adopt different conformational geometries around metal centers is of particular note. DbaPHOS (127) was found to act as a cis- and trans-chelating bisphosphine in both square planar PdII and PtII complexes. The 1,4-dien-3-one motif is hemilabile; exchange between coordinated and non-coordinated alkenes is observed in both the Pd0 complex, 167, and the related cationic CuI complex, 193. An investigation into the CuI complexes’ activity in the cyclopropanation of styrene, as catalysts, showed that they are commensurate with other recently reported systems. In addition to the coordination chemistry of the novel ligand systems, some interesting findings emerged in the ligand synthesis and characterisation studies. For example, monodbaTHIOPHOS (149) undergoes an interesting solid-state [2+2] intramolecular cycloaddition transformation, giving cycloadduct, 206. Furthermore, 2-hydroperoxytetrahydrofuran was found to be an impurity in the microwave-assisted Horner-Wadsworth-Emmons reaction of 2-(diphenylthiophosphine)benzaldehyde (136) with 1,3-bis-(ethoxyphosphonato)-acetone (130) to give of dbaTHIOPHOS (137) and an unexpected THF insertion product, 138. The latter is explained by a side reaction involving the reduced compound, tetrahydrofuran-2-ol, derived from 2-hydroperoxytetrahydrofuran.

This investigation is based on the topotactic reduction reactions of 3 sets of phases: La₁-ₓSrₓMnO₃ (0.6 ≤ x ≤ 1), La₁-ₓCaₓMnO₃ (0.6 ≤ x ≤ 1) and Sr₃Fe₂-ₓCoₓO₅Cl₂ (0 ≤ x ≤ 1). The topotactic reduction reactions of La₁-ₓSrₓMnO₃ (0.6 ≤ x ≤ 1) perovskite phases using NaH as a solid state reducing agent result in the formation of reduced phases which contain manganese centres with a constant average oxidation state of +2.5, thus leading to an empirical composition of La₁-ₓSrₓMnO₃-(0.5+x)/2. The structures of the reduced phases contain a 6-layer OOTOOT’ stacking sequence of the octahedral (O) and tetrahedral (T) sheets and so are closely related to the 4-layer OTOT’-stacked brownmillerite structure. Close inspection reveals that the structures of the La₁-ₓSrₓMnO₃-y (x = 0.67, 0.7 and 0.75) reduced phases contain an intralayer ordered arrangement of twisted tetrahedral chains, and are the first instances of refined 6-layer structures containing such an arrangement. The driving force dictating the arrangement of the twisted tetrahedral chains in these 6-layer structures are shown to be the size of the tetrahedral chain dipole moment and the coupling between neighbouring tetrahedral layers in a similar manner to the brownmillerite structure. This logic has been applied to rationalise the ordering arrangement of the twisted tetrahedral chains in other structures containing tetrahedral layers. Variable temperature neutron diffraction data reveal that the La₁-ₓSrₓMnO₃-y (0.67 ≤ x ≤ 0.83) reduced phases adopt magnetically ordered structures incommensurate with the nuclear structures below TN. In contrast, the structures adopted by reduced phases formed by topotactic reduction reactions of La₁-ₓCaₓMnO₃ (0.6 ≤ x ≤ 1) perovskite phases using NaH are split into 2 groups as a function of the La:Ca ratio: The reduction of perovskite phases in the range (0.6 ≤ x ≤ 0.8) result in the formation of reduced phases with an empirical composition of La₁-ₓCaₓMnO₂ which adopt structures containing a disordered arrangement of layers of edge-sharing MnO₆ octahedra and layers of vertex-sharing MnO₄ tetrahedra. In contrast, reduction of the perovskite phases in the range (0.9 ≤ x ≤ 1) result in the formation of reduced phases with an empirical composition of (La₁-ₓCₓx)0.5MnO which adopt the rock salt structure with a disordered arrangement of the cations. The (x < 1) reduced phases are the first reported examples of extended oxides which contain manganese centres with an average oxidation state of below 2. Variable temperature neutron diffraction data reveal that the La₁-ₓCaₓMnO₃-y (x= 0.6, 0.67 and 0.7) reduced phases adopt G-type antiferromagnetically ordered magnetic structures below approximately TN ~ 220 K. The structure of Sr₃Fe₂O₅Cl₂ is closely related to that of the A₃B₂O₇ n = 2 Ruddlesden-Popper structure. The topotactic reduction reaction of Sr₃Fe₂O₅Cl₂ with LiH results in the formation of the Fe(II) phase Sr₃Fe₂O₄Cl₂. Neutron powder diffraction data show that Sr₃Fe₂O₄Cl₂ adopts a body-centred tetragonal crystal structure with anion vacancies located within the central SrO layer of the phase. The structure of Sr₃Fe₂O₄Cl₂ is therefore a rare example of a structure consisting of infinite sheets of corner-sharing Fe(II)O₄ square planes. In addition, the effect of cobalt-doping on the magnetic properties of the isostructural Sr₃Fe₂-ₓCoₓO₄Cl₂ (0 ≤ x ≤ 1) series of reduced phases was investigated. Cobalt-doping was found to frustrate the antiferromagnetic order initially leading to a decrease in the magnetic ordering temperature but ultimately leading to spin glass behaviour.

The development of novel ligands for the complexation of transition metal ions in inorganic chemistry is a rapidly developing field of study. The broad objective of this work is to design novel tripodal transition metal based receptors of (TPA) frame work which can act as hosts for small molecules (guests) e.g. fluoride and succinate. In addition, investigation into the co-ordination chemistry of those receptors with first row transition metals were explored using variety of characterizing techniques such as: Infrared Spectroscopy (IR), Electronic transitions (UV-Vis), Mass Spectrometry (MS), Nuclear Magnetic Resonance (NMR), Cyclic voltammetry (CV) and Single Crystal Diffractometer (X-Ray). Mono, Bis and Tris thiourea tripodal ligands have been synthesised and their co ordination chemistry has been investigated (chapter 2, 3 and 4) as well as the binding studies of the bisthiourea (chapter 3) to bind: fluoride and succinate using *H NMR titration technique. The co-ordination chemistry of TPPA with some first row transition metals has been studied and it was expected to show high affinity for seven coordination sphere and indeed it has shown strong preference for mono capped octahedral geometry (chapter 5).

The majority of the work described in this thesis focuses on the development of a new synthetic route to binary and ternary intermetallic compounds, which avoids the need for reaction at very high temperatures, multi-step reactions, reaction under vacuum and/or the synthesis of precursors. The route was adapted from a synthetic route reported for the synthesis of ternary and quaternary nitrides adopting the ε-carbide and filled β-manganese structures, where mixed metal oxides were reduced under an atmosphere of 10% hydrogen in nitrogen. In this work, binary intermetallic compounds including metal antimonides, germanides and bismuthides were prepared by reducing mixed metal oxides under 10% hydrogen in argon. A variety of high purity antimonides were synthesised, including NiSb, CoSb, CoSb3, Cu2Sb and SnSb. Tailoring of some of the properties of these antimonides was attempted by introducing other atoms into the crystal structures, thereby forming ternary compounds. The most notable ternary antimonides prepared include the solid solution of NiSb in CoSb, and the solid solution of RhSb3 in CoSb3. The Sb-Sb bond lengths in the solid solution of NiSb in CoSb display an unexpected trend, passing through a minimum. Reasons for this based on electronic grounds are suggested. Notably the Te-Te bond length within the solid solution of NiTe in CoTe does not display this variation. The solid solution of RhSb3 in CoSb3 is potentially very useful as the introduction of rhodium into the structure may alter the thermoelectric behaviour of the material. However, thermoelectric measurements on the compounds are yet to be carried out. Other work described in this thesis focuses on attempts to synthesise transition metal nitrides, firstly by extending a synthetic route reported for the synthesis of ε-carbide and filled β-manganese nitrides by introducing germanium into Fe3Mo3N, Co3Mo3N and the hypothetical compound "Ni3Mo3N", and secondly by the thermal treatment of potential precursors to binary transition metal nitrides. The synthesis and magnetic properties of Fe2GeMo3N, Co2GeMo3N and Ni2GeMo3N are discussed, and the synthesis of solid solutions of Fe2GeMo3N and Ni2GeMo3N in Co2GeMo3N are described. In addition, experiments to determine whether a small interstitial (in this case nitrogen) is needed to stabilise certain compounds adopting the ε-carbide and filled β-manganese structures are described. The preparation, crystal structures and thermal treatment of metal urea complexes as potential precursors to binary nitrides are also discussed. Two of the metal urea complexes synthesised, ([Cr(urea)4(H2O)2][NO3]3 and [Fe(urea)6][NO3]), are particularly interesting: [Cr(urea)4(H2O)2][NO3]3 crystallises in a primitive, but close to C-centred unit cell, and [Fe(urea)6][NO3]3 crystallises in a C-centred cell which is related by a five-fold expansion to a smaller pseudo C-centred cell previously reported for the same structure.

The Thesis is based upon the development of novel synthetic strategies towards heteroatom substituted boranes. The strategies that have been developed and their application towards the synthesis of new species and their characterisation are discussed. The first chapter contains the introduction and explains the basic concepts of boron cluster chemistry and a brief summary of their applications. A discussion of existing strategies toward the synthesis of heteroatom substituted boranes follows together with a description of those complexes already synthesised and characterised. The second chapter describes the development of high yield syntheses ofnido- [7-PBioHi2]~ and c/o5o-l,2-P2Bi0Hio; important phosphaborane starting materials that had previously only been made in low yield. The third chapter concerns the exploration of the chemistry of the two clusters whose synthesis is described in chapter 2. This includes alkyl substitution ofnido- [7,8-P2B9Hio]~ and the synthesis of several new mixed heteroatom species including closo-l,23-EP2B9R9 (E = Ge, Sn and Pb), c/o50-[l,2-SnPBi0Hi 0]" and c/ojo-l-R-1,2- SiPBioHio (R = Me or H). A study of the multiple alkylation of mWo-[7-PBi0Hi 0]3~ is also described in this chapter. The fourth chapter contains a summary of phosphacarborane chemistry, a description of modifications to the existing synthesis of closo-l,2-PCB\oH\i to allow isolation of larger quantities and some unsuccessful synthetic attempts to synthesize c/

This Thesis is concerned with the development of high yield synthetic strategies to phosphaboranes and phosphacarboranes. These compounds have attracted attention due to their potential as single-source precursors for the deposition of thin films of doped boron carbide via plasma enhanced chemical vapour deposition. It has shown that suitable doping of the boron carbide can lead to wide band gap semiconductors and incorporation of phosphorus into the cage structure of the solid-state material is one way of achieving this aim. Chapter one discusses the chemical vapour deposition of boron carbide and goes on to describe its uses as neutron detectors and semiconductors. Chapter two presents the existing methods used for the synthesis of aminophosphines and highlights the importance of two such species, PH(NBus2)2 and PCl2N(CJln)2 . The remaining chapters cover the experimental work used for the preparation of phosphaboranes and phosphacarboranes that contain the phosphorus atom as a vertex. Chapter three focuses on the reaction of bis(dialkylamino)phosphines with decaborane and describes the synthesis of the nido-[l-nido-?^\o\\\2\ anion in high yield. In Chapter four, the use of the nido-[l-PB}oH\2\ anion to prepare a range of cluster complexes via reaction with a variety of electrophiles is discussed. Chapter five focuses on the reaction of bis(dialkylamino)phosphines with nido-5,6- dicarbadecaborane(12) and describes the synthesis of novel compounds of the formulae 6,9-R2NHP-5,6-C2 Bs Hn, (R = Pr', Bu1 ). This is considered as an intermediate product which subsequently gives a mixture of the nit/<>-7,8,\ 1- PC2B8Hn, mWo-[7,8,9-PC;>BxHio]~ and /m/o-[7,8,l 1-PC:B8 H IO ] species whose ratio is dependant on the R group. Each chapter contains a brief introduction, discusses the results obtained including multinuclear NMR spectroscopy and crystal structure data and concludes with an experimental section.

MgH2 is hydrogen dense but normally has a rutile structure, which is too stable with too low a hydrogen diffusion rate for practical applications. At pressures of several GPa a CaF2 structure phase has been predicted for MgH2 . With a small fraction of the magnesium atoms substituted by transition metal atoms such as Ti, this cubic phase remains stable when the high GPa synthetic pressure is released with typical composition MgyTiHie- How the metal-hydrogen bonding differs from that in the conventional MgH2 and TiH2 has been investigated in this work. Using Electron Localisation Function topological analysis, the site preference for hydrogen entering the host lattice can be predicted. Vibrational spectra have been calculated with Density Functional Theory (DFT) with the aim of modelling the incoherent inelastic neutron scattering spectra, which have been measured at the TOSCA spectrometer at ISIS. DFT calculations show a weakening in the force constants of the Ti-H and Mg-H bond which can be directly related to the FCC structures of TiH2 and MgH2 . The structural similarities of the three FCC systems lead to a better understanding of the formation process of the new ternary compounds. The presence of two non-equivalent types of tetrahedral site with different force constants resulting from the normal modes of vibration suggests a twostep hydrogenation and dehydrogenation process. Comparison with the TiHx system is also interesting in terms of hydrogen diffusion inside the host lattice and a quasi-elastic neutron scattering experiment has been carried out to investigate this. Gravimetric measurements allow us to investigate the reversibility of incompletely dehydrogenated samples and results showing the fast kinetics are presented. If the partial reversibility could be optimised with respect to TM selection and addition, it would mean a breakthrough for storing hydrogen in magnesium hydrides.

Many interesting and often exotic magnetic phenomena have been observed over the past twenty years in the family of the heavy metal pyrochlore oxides, A2B2O6O’. In these systems, competing interactions are common and tend to emerge mainly at low temperatures. Magnetic properties are related to the contribution of d orbitals that transition metal (TM) offer and their interplay with the positive contribution coming from the cation sitting on the A site. The work described in this thesis explores the effects of chemical substitution of the A site cation on the symmetry and the properties of a number of pyrochlores containing TM of the second and third transition row, such as Ir, Ru, Mo and Os. Depending if this site is fully occupied and on the radius size the behaviour of the resulting material can change significantly. The defect pyrochlore family AOs2O6 (A = Cs, Rb, K) was studied in detail following the attention that its members attracted for having been the first materials, belonging to this subgroup, to exhibit superconducting properties [1, 2, 3] and for the diversity in their properties. In these compounds, the smaller the ionic radius of an element, the weaker is the bond to the structure. As a result, the temperature dependence of their energy becomes quite different from normal lattice vibrations and gives interesting low temperature behaviours. The effect of replacing the weak bonded potassium ions on the structures and superconducting properties of the AOs2O6 phases has also been studied. The ability to exchange the A-type in pyrochlores is well known and leads to applications for example in nuclear clean-up. Thus the ion exchange of K+ by smaller cations such as Li+ or Na+ has been investigated with the aim of synthesising compounds which cannot be obtained by direct synthesis. New defect pyrochlore materials, AA’Os2O6 (A’ = Li+, Na+) have been synthesised together with hydrated derivatives, AA’OsO6.nH2O. Parent materials were obtained by ion exchange in non-aqueous solvents under strictly dry conditions. A Ba-based osmium oxide pyrochlore, Ba(Os2O6)2.H2O was also synthesised, for the first time, from the K-osmate starting material by ion-exchange methods in aqueous medium. In this work, diffraction techniques, X- ray and neutron powder diffraction, were employed and found suitable for detecting the change in cation and anion location and general structure investigation.These structural descriptions are correlated with the measured superconducting properties and theoretical descriptions of variations in the Tc in these systems as a function of cation size and rattling.