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Despite the widespread use of well-defined Pd II complexes as pre-catalysts for cross-coupling processes, the role of the throw-away ligand is still underexplored. In this work we focused on the complexes of the type [Pd(NHC)(η 3 -R-allyl)Cl] (NHC = N-heterocyclic carbene) and we investigated the influence of the R substitution on the allyl moiety. Starting from the already described [Pd(IPr)(η 3 -cinnamyl)Cl] and [Pd(IPr*)(η 3 -cinnamyl)Cl] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, IPr* = N , N '-1,3-bis[2,6-bis(diphenylmethyl)-4-methylphenyl]imidazol-2-ylidene) we prepared eight new complexes bearing new substitutions on the cinnamyl motif and we tested them in the C-N bond formation to evaluate the effect of the throw-away ligand modification in the catalytic activity. In addition, we studied the undesired formation of the less active off-cycle [PdI2(NHC) 2 (η 3 -R-allyl)(μ-Cl)] dimers from the corresponding Pd II complexes to evaluate the role of the new throw-away ligands on the inhibition of this process.

The intricate σ and π-bonding of N-heterocyclic carbenes (NHCs) to metals and the need to quantify their electronic properties to rationalize reactivity of complexes have resulted in the creation of numerous methodologies to understand the NHC-metal interaction which are, as we now show, flawed. Our search for a unified, easily accessible system to gauge these fundamental properties has resulted in the discovery of two systems that highlight the flaws present in existing systems and provide a more accurate measure of the NHC ligand electronic properties.

Carbene-metal-amide (CMA) complexes of gold, silver, and copper have been studied extensively for their photochemical/photocatalytic properties and as potential (pre-)catalysts in organic synthesis. Herein, the design, synthesis, and characterization of five bench-stable Au-, Ag-, and Cu-NHC complexes bearing the benzotriazolyl anion as an amide donor, are reported. All complexes are synthesized in a facile and straightforward manner, using mild conditions. The catalytic activity of the Ag and Cu complexes was studied in propargylamide cycloisomerization and carbonyl hydrosilylation reactions. Both CMA-catalyzed transformations proceed under mild conditions and are highly efficient for a range of propargylamides and carbonyl compounds, respectively, affording the desired corresponding products in good to excellent yields.

A series of novel dinuclear NHC-gold-thiolato and -alkynyl complexes bearing aromatic linkers were successfully synthesized by an efficient and simple synthetic route. The catalytic activity of these complexes was tested in a lactonization reaction. The reaction proceeds in high efficiency, in short reaction time and under mild conditions, and is complementary to existing methods. Furthermore, the digold(I)-thiolato derivatives exhibit remarkable cytotoxicity towards several cancer cell lines.

The 4-RN-1,3-Ar 2 -imidazolium salt, R = iPr, t Bu, Ar = Mes, Dipp, Mes = mesityl, Dipp = 2,6-bis-diisopropyl-phenyl was metalated by Au I at the C2-, C5- and 4-RN positions depending on the reactants and conditions employed; a rare direct rearrangement of a Au I aminide to an abnormal imidazol-5-ylidene Au I complex was also observed and based on a DFT study it may involve TfO - facilitated H + transfer.

Green and sustainable access to chiral and achiral gold-IBiox complexes is reported. The gold complexes were synthesized using a simple, air-tolerant, weak base protocol carried out in a green solvent. Their catalytic activity was examined in the hydroamination of alkynes. The steric protection afforded the gold center by these ligands was quantified using the % V bur model and compared with the most commonly encountered NHCs.

The synthesis of novel phosphine palladium PEPPSI and dimer complexes bearing RuPhos, SPhos and XPhos phosphines is reported. The crystal structures of XPhos Pd PEPPSI with pyridine, SPhos Pd PEPPSI with 3-chloropyridine as throw-away ligands and the RuPhos palladium dimer were obtained and compared with previously reported congeners. The catalytic activity of these novel complexes was examined via a C-N coupling reaction involving 4-chloroanisole and morpholine. RuPhos complex 2b proved most active, leading to 97% yield with a low (0.2 mol%) catalyst loading, while phosphine palladium dimers showed significantly lower catalytic activity. However, the addition of 3-pentanone as an activator/stabilizer significantly improved the yields of phosphine dimers and PEPPSI complexes when the reactions were performed in THF.

In our search for simple synthetic routes to N -heterocyclic carbene (NHC)-metal complexes and their derivatives, we herein report an operationally simple, expedient and scalable method to obtain the widely used NHC-metal-diketonates. The reported complexes are synthesized for the first time under mild, aerobic conditions and in excellent yields in a sustainable manner. The protocol is general with regards to the anionic co-ligand and the ancillary carbene ligands. The spectroscopic and crystallographic characterization of the complexes reveal a bidentate binding mode of the diketonate ligand to copper while the gold-congener is C-bound. Finally, the reported Au complex was shown to be an efficient pre-catalyst for the hydrocarboxylation of alkynes.

A sustainable and facile weak-base synthetic route to platinum N-heterocyclic carbene (NHC) complexes is disclosed. The mechanism of this reaction is also elucidated via experimental and computational investigations. This straightforward protocol is then used for the synthesis of novel Pt(II)-NHC complexes and its utility is further explored to access key Pt(0)-NHC precatalysts.

We have investigated the reactions of chalcogenoureas derived from N -heterocyclic carbenes, referred to here as [E(NHC)], with halogens. Depending on the structure of the chalcogenourea and the identity of the halogen, a diverse range of reactivity was observed and a corresponding range of structures was obtained. Cyclic voltammetry was carried out to characterise the oxidation and reduction potentials of these [E(NHC)] species; selenoureas were found to be easier to oxidise than the corresponding thioureas. In some cases, a correlation was found between the oxidation potential of these compounds and the electronic properties of the corresponding NHC. The reactivity of these chalcogenoureas with different halogenating reagents (Br 2 , SO 2 Cl 2 , I 2 ) was then investigated, and products were characterised using NMR spectroscopy and single-crystal X-ray diffraction. X-ray analyses elucidated the solid-state coordination types of the obtained products, showing that a variety of possible adducts can be obtained. In some cases, we were able to extrapolate a structure/activity correlation to explain the observed trends in reactivity and oxidation potentials.

A simple synthetic pathway to Au-NHC amido complexes is described. Syntheses and isolation of [Au(NHC)(NR 1 R 2 )] complexes, bearing various NHC ligands and NH-containing heterocycles under mild conditions are reported. The in vitro anticancer activity of these gold-complexes was investigated on three human cancer cell lines. A number of these show comparable or even better antiproliferative activity than cisplatin. Noteworthy is the non-toxicity of most of the complexes on normal cells.

Synthetic access to monomeric copper-alkynyl and copper-thiolato complexes of the type [(NHC)Cu(R)] (R = alkynyl or thiolato) using a weak base approach is reported. All reported reactions proceed under mild conditions in air and in environmentally acceptable solvents. The novel complexes are fully characterized and single crystal X-ray analyses unambiguously establish the atom connectivity in these mononuclear complexes. The importance of the supporting NHC ligand's steric properties in stabilizing mononuclear complexes is discussed.

The self-assembly of bis-tridentate ligands leads to the spontaneous formation of [2 × 2] grid-like metal complexes. However, the synthesis of such ligands is rather cumbersome. In the work, we demonstrate a straightforward synthesis route to prepare bis-tridentate 4,6-bis((1H-1,2,3-triazol-4-yl)-pyridin-2-yl)-2-phenylpyrimidine ligands through double CuAAC click chemistry with 4,6-bis(6-ethynylpyridin-2-yl)-2-phenylpyrimidine as well as their self-assembly into [2 × 2] grid-like metal complexes. In addition, four macromolecular ligands were synthesized starting from azido-end-functionalized poly(2-ethyl-2-oxazoline) (PEtOx) or poly(ethylene glycol) (PEG). These macromolecular ligands were used in the construction of star-shaped supramolecular polymers through complexation with transition metal ions (e.g., Fe2+ or Zn2+). The successful fabrication of complexes and star-shaped polymers was confirmed by UV-vis titration measurements and MALDI-TOF mass spectrometry. However, the chemical structure of the polymer was found to have a strong influence on the [2 × 2] grid formation, which was successful with the PEG-ligands but not with the PEtOx-ligands, while the molecular weight of the PEG did not interfere with grid formation.

A simple and efficient synthetic route to [RuCl 2 (NHC)(p-cymene)] and [Ru(CO 3 )(NHC)(p-cymene)] complexes making use of a weak base, under aerobic conditions, is reported. This method enables access to a series of NHC-ruthenium compounds with moderate to good yields under mild conditions. The Ru pre-catalysts were successfully used in olefin oxidation catalysis at low catalyst loading and reach complete conversion in short times.

A general, user-friendly synthetic route to [Pt(NHC)(L)Cl2] and [Pt(NHC)(dvtms)] (L = DMS, Py; DMS = dimethyl sulfide, dvtms = divinyltetramethylsiloxane, Py = pyridine) complexes has been developed. The procedure is applicable to a wide range of ligands and enables facile synthetic access to key Pt(0)- and Pt(ii)-NHC complexes used in hydrosilylation catalysis.

Tri(1-adamantyl)phosphine (PAd3) possesses unique steric and electronic properties positioning it at the border between tertiary phosphines and N-heterocyclic carbenes (NHC). Novel Au-PAd3 complexes were synthesized from the known [Au(PAd3)Cl]. We have optimised reaction conditions for the synthesis of this useful synthon in order to circumvent the formation of the [Au(PAd3)2]Cl. [Au(PAd3)Cl] was used to access a number of derivatives and some were deployed as catalysts. The hydration of alkynes was targeted to gauge the reactivity of Au-PAd3 complexes and permit comparison with NHC and tertiary phosphine congeners.

Chalcogen-based urea compounds supported by a wide range of N-heterocyclic carbenes are synthesised and fully characterised. Coordination of selenoureas is further explored with Group 11 transition metals to form new copper, gold and silver complexes. Single crystal X-ray analyses unambiguously establish the solid-state coordination of these complexes and show that the geometry of a complex is highly influenced by a combination of electronic properties - mainly π-accepting ability - and steric hindrance of the ligands, as well as the nature of the metal, affording a variety of coordination behaviours. In this report, we investigate these phenomena using several experimental methods.

In this work we report a novel lanthanide octamolybdate 1D chain type of structure formed with holmium, thulium and lutetium. This is a rare case of compounds built out of [Mo8O28]8- units. These compounds were prepared in a mild reaction synthesis starting from the commonly used heptamolybdate polyoxometalate (POM) [(NH4)6[Mo7O24]. Interestingly, in our previous study we have employed a very similar synthesis route for lanthanides with a larger ionic radius and obtained heptamolybdate clusters. For the lanthanides with a smaller ionic radius (Ho3+, Tm3+ and Lu3+) no crystals could be obtained under those conditions. Only when doubling the amount of the lanthanide salt, single crystals suitable for measurements were obtained. These crystals revealed yet a very different structure from those previously observed. Lanthanide octamolybdate 1D chains were formed. Doubling the amount of the salt for other lanthanide ions still yielded heptamolybdate compounds previously reported by us. The lutetium octamolybdate compound was doped with 1-7.5% of Eu3+ ions yielding emission colors ranging from blue to strong red. Additionally in these materials the excitation wavelength was varied, and it was observed that the materials emission color was excitation-wavelength dependent.

In the last decade, deep eutectic solvents (DES) have risen as promising and cheap alternatives for the often expensive and moisture-sensitive ionic liquids. For the application in metal processing industries such as hard chrome plating, still very little is known of the behavior of metal ions in these types of liquids. Therefore, we use the model-free Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) method to study Cr(iii) as sustainable alternative to the hazardous Cr(vi) and obtain reference UV/Vis spectra of chromium(iii)chlorides in several aqueous solutions and in water-DES mixtures. In addition, the results have been confirmed by EXAFS measurements. We observe that in the DES ethaline, ethylene glycol ligands are coordinating with the chromium(iii) metal ions and hence, different UV/Vis reference spectra are obtained, compared to those in aqueous solutions. Additionally, concentration profiles provide a tool for tuning the coordination chemistry, based on the choice of the appropriate DES mixture or aqueous solutions. Consequently, valuable UV/Vis reference spectra for some known and unknown chromium chloride complexes in several aqueous solutions and DES-water mixtures were obtained, which showed that the coordination chemistry in these liquids can be considerably different and comparison should be done with great care.

We describe the synthesis and characterisation of a series of new copper and silver complexes with selenourea ligands derived from common and readily-prepared N-heterocyclic carbenes (NHCs). The copper complexes behave somewhat predictably, typically leading to [CuCl(L)] complexes (with two exceptions). The silver complexes display a diverse range of structural motifs, including [AgCl(μ-L)] 2 , [AgCl(L) 2 ], [Ag(L) 2 ] + , [Ag(L) 3 ] + , and [(Ag(L) 2 ) 2 (μ-L)] 2+ species. All new complexes are characterised by multinuclear NMR spectroscopy, and several examples are characterised by X-ray crystallography. This study demonstrates the diversity of coordination behaviour that these selenourea ligands can engage in.

The hydrothermal reactions of 1,2,4,5-cyclohexanetetracarboxylic acid (H 4 L) with CoCl 2 ·2H 2 O and rigid or semi-rigid bis(imidazole) ligands were able to generate two Co(ii) coordination polymers (CPs), {[Co 5 (L) 2 (1,4-bimb)(μ 3 -OH) 2 (H 2 O) 8 ]·2H 2 O} n (1), {[Co(L) 0.5 (1,4-bib)]·H 2 O} n (2) (1,4-bimb = 1,4-bis(imidazol-1-ylmethyl)benzene, 1,4-bib = 1,4-bis(1H-imidazol-1-yl)benzene). CPs 1 and 2 were structurally characterized by elemental analysis, IR spectroscopy, X-ray powder diffraction and single crystal X-ray diffraction. CP 1 features a 3D 3,3,4,4,5-connected framework with an unprecedented {4 2 ·8·10 2 ·12}{4 3 ·6·8 6 } 2 {4 3 } 2 {4 6 } 2 {6 2 ·8} 2 topology, which represents the first example of CPs with such a topology. CP 2 possesses a three-fold interpenetration 3D framework with mog topology. The distinct structures of the two CPs may result from diverse coordination modes of the (L) 4- ligands and different structural characteristics of rigid or semi-rigid N-donor ligands. The thermal stabilities, photoluminescence properties and electrochemical behavior in the solid state for CPs 1 and 2 have been investigated. The photophysical studies indicated that CPs 1 and 2 are potential semiconductive materials. Moreover, both CPs 1 and 2 show high photocatalytic efficiency for the degradation of methylene blue (MB) under UV light irradiation and exhibit good stability and recyclability. A possible photocatalytic mechanism is speculated by introducing t-butyl alcohol (TBA) as a widely used ˙OH scavenger.

Six Co(ii)-based coordination polymers (CPs) with characteristic frameworks and topologies-namely, [Co(L1)(DCTP)] n (1), [Co(L2)(DCTP)] n (2), [Co(L3)(DCTP)] n (3), {[Co 3 (L4) 3 (DCTP) 3 ·H 2 O]·H 2 O} n (4), [Co(L5) 1.5 (DCTP)] n (5) and [Co(L6)(DCTP)] n (6)-were successfully hydrothermally synthesized by employing the halogenated linear ligand 2,5-dichloroterephthalic acid (H 2 DCTP). The interpenetrated structures could be rationally modulated by auxiliary N-donor co-ligands containing 1,1'-(1,4-butanediyl)bis-1H-benzimidazole (L1), 1,4-bis(5,6-dimethylbenzimidazol-1-yl)-2-butylene (L2), 1,2-bis(2-methylbenzimidazol-1-ylmethyl)benzene (L3), 1,4-bis(2-methylbenzimidazol-1-ylmethyl)benzene (L4), 1,2-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene (L5) and 1,4-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene (L6). These diaphanous crystals were clearly characterized by elemental analysis, infrared (IR) spectra and X-ray powder diffraction (XRPD) as well as single-crystal X-ray diffraction analysis. With the aid of the flexible N-donor co-ligands, CP 1 occupies a non-interpenetrated 2D sheet with the point symbol {4 4 ·6 2 } sql net topology, CP 2 possesses a 3D hexagon-shaped network with the point symbol {6 6 } three-fold interpenetrated sqc6 topology, CP 3 exhibits a 2D layer with the point symbol {4 4 ·6 2 } sql net topology, CP 4 reveals an unusual 3D framework with the point symbol {4 2 ·6 3 ·8} three-fold interpenetrated sra topology, CP 5 has a 3D hexagon-shaped network with the point symbol {6 6 } two-fold interpenetrated sqc6 topology, while CP 6 displays a 3D hexagon-shaped network with the point symbol {6 6 } three-fold interpenetrated sqc6 topology. The diverse structures of CPs 1-6 illustrate that the substitute group and position of the methyl group of the bis(benzimidazole) derivatives play a significant role in the assembly of such interpenetrated frameworks. Moreover, luminescence properties and thermal behavior, as well as the electrochemical and photocatalytic properties of CPs 1-6 on the degradation of methylene blue, are also presented.

Two Cu(i) cyanide coordination polymers (CPs), namely, [Cu 2 (L1)(CN) 2 ] n (1) and [Cu 2 (L2)(CN) 2 ] n (2) (L1 = 4,4'-bis(2-methylbenzimidazol-1-ylmethyl)biphenyl, L2 = 4,4'-bis(5,6-dimethylbenzimidazol-1-ylmethyl)biphenyl) were synthesized and structurally characterized by single crystal X-ray diffraction, IR spectroscopy, X-ray powder diffraction and elemental analysis. The cyanide ligands in these CPs are generated in situ from the C-C bond cleavage of acetonitrile under solvothermal conditions, which is environmentally friendly and used conveniently. CP 1 features a three-fold interpenetration 3D framework consisting of Cu 10 (CN) 6 (L1) 4 rings, which represents the first investigation on introducing bis(benzimidazole) ligands into copper(i) cyanide CPs with ThSi 2 topology, while CP 2 exhibits a two-dimensional (6,3) layered structure containing Cu 6 (CN) 4 (L2) 2 rings. The thermal stabilities, and photoluminescence and electrochemical behavior in the solid state of CPs 1 and 2 have been investigated in detail. Moreover, both CP 1 and CP 2 manifest promising photocatalytic activities (photodegradation efficiency using CP 1 is 90.8% and using CP 2 is 87.2%) for the degradation of methylene blue (MB) under UV light irradiation. A possible photocatalytic mechanism is suggested by introducing t-butyl alcohol (TBA) as a widely used ˙OH scavenger.

A 3D 4-coordinated self-catenated metal-organic framework {[Co(bibp)(1,4-chdc)]·2H2O}n (1) (bibp = 4,4'-bis(1-imidazolyl)biphenyl, 1,4-H2chdc = 1,4-cyclohexanedicarboxylic acid) has been synthesized by hydrothermal reaction and its structure has been determined. This framework buries an unprecedented 4-coordinated self-catenated net that can be represented as an array of honeycomb-like units catenated in an inclined mode, with the highest topological density among the 4-coordinated nets that occur in crystal structures. Additionally, the thermogravimetric, photo-catalytic and electrochemical behaviors have been investigated.

Nano-sized particles of monoclinic-LaVO4 were prepared in a short reaction time of 30 minutes by employing a microwave assisted hydrothermal synthesis in the presence of glycerol, which was used both as a solvent and structure-directing agent. The tetragonal-LaVO4 is known to show strong luminescence properties when doped with Ln(3+), whereas the monoclinic-LaVO4 is usually considered not suitable for luminescence and therefore luminescence properties of monoclinic-LaVO4 doped with Ln(3+) ions are seldom investigated. Due to the scarce amount of research on the topic of luminescence of Ln(3+) doped monoclinic-LaVO4 in this paper a detailed study of solid state luminescence properties, including quantum yields, of nano-sized monoclinic-LaVO4 doped with different molar percentages of Eu(3+) is presented. It was observed that the 12.5%Eu(3+) doped sample showed the strongest luminescence properties. Additionally a study of the influence of different rare-earth ions (Y(3+), Gd(3+), Lu(3+)) co-doped into the particles was performed in order to explore the potential of increasing the luminescence of these materials. Furthermore stable colloidal suspensions of the Eu(3+) doped monoclinic-LaVO4 nanoparticles showing strong red emission could be obtained.

Microstructured Y2WO6 materials were prepared in a hydrothermal synthesis in the presence of glycerol, which was employed as both a solvent and a structure directing agent, after which they were heat treated at 1100 °C. These materials, similar to other previously reported Y2WO6 as well as other rare-earth tungstate structures, showed interesting luminescence properties. Six Ln(3+) doped or co-doped samples, which showed white light emission, are described in this paper. It was observed that the doping ion(s)/doping percentage, heat treatment of the material, as well as the chosen excitation wavelength could be used to tune the emission color of the samples to obtain white light with a warmer or colder undertone. The luminescence lifetimes, quantum yields, CIE coordinates and correlated color temperatures for these samples were determined. Additionally, for the co-doped Y2WO6 samples the energy transfer mechanisms were proposed because a significant change in the luminescence properties was observed after heat treatment. This can be linked to the conversion from distorted tungstate groups in the precursor material to regular tungstate groups in the heat treated material.

We report on the synthesis and characterization of second generation ruthenium indenylidene catalysts bearing unsymmetrical N-heterocyclic carbene (NHC) ligands denoted as RuCl2(3-phenyl-1-indenylidene)(1-mesityl-3-R-4,5-dihydroimidazol-2-ylidene)(PCy3), in which R is methyl 8a, octyl 8b or cyclohexyl 8c. The characterization of 8a-c was performed by NMR spectroscopy, elemental analysis, IR, HRMS and single-crystal X-ray diffraction analysis. In addition, the catalytic activity of the obtained initiators was evaluated in various representative metathesis reactions. The results reveal that the complexes 8a-c, bearing an N-alkyl side on the NHC, show a faster catalytic initiation than the reference complex 2. Complex 8a, which performs the best among the investigated indenylidene complexes, exhibits slower initiation but better overall efficiency than its benzylidene analogue 1c, especially in a low catalyst loading.

In this paper, various microstructures of Ce2(WO4)3 and Ce10W22O81 were prepared by applying a hydrothermal synthesis, in a ligand-free environment, and in the presence of a dioctyl sodium sulfosuccinate (DSS) surfactant, after which the materials were heat treated at a temperature of 900 °C. Depending on the ratio of cerium ions to sodium tungstate, as well as the reaction pH, two different cerium tungstate materials were obtained. The source of cerium, and the presence or absence of the surfactant had a significant influence on the morphology of the final product. The photoluminescence properties of Tb(3+) doped cerium tungstate materials were investigated. Luminescence measurements showed an efficient charge transfer from the tungstate groups to the Tb(3+) ions. All the materials emitted blue or green light under UV excitation.

The first examples of structurally characterised mixed-ligand metal-containing ionic liquids (ILs) are presented, synthesised by the use of different N-alkylimidazoles. The cations consist of two-coordinate silver(i) centres ligated by two different N-alkylimidazole ligands. It is shown that the resulting ionic liquids have lower melting points than the single ligand ILs.

Ionogels are solid oxide host networks confining at a meso-scale ionic liquids, and retaining their liquid nature. Ionogels were obtained by dissolving lanthanide(III) complexes in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C6mim][Tf2N], followed by confinement of the lanthanide-doped ionic liquid mixtures in the pores of a nano-porous silica network. [C6mim][Ln(tta)4], where tta is 2-thenoyltrifluoroacetonate and Ln=Nd, Sm, Eu, Ho, Er, Yb, and [choline]3[Tb(dpa)3], where dpa=pyridine-2,6-dicarboxylate (dipicolinate), were chosen as the lanthanide complexes. The ionogels are luminescent, ion-conductive inorganic-organic hybrid materials. Depending on the lanthanide(III) ion, emission in the visible or the near-infrared regions of the electromagnetic spectrum was observed. The work presented herein highlights that the confinement did not disturb the first coordination sphere of the lanthanide ions and also showed the excellent luminescence performance of the lanthanide tetrakis beta-diketonate complexes. The crystal structures of the complexes [C6mim][Yb(tta)4] and [choline]3[Tb(dpa)3] are reported.