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Iron(II) bonded over an oxo surface modeled by calix[4]arene shows unusual reactivity and binding abilities resulting in the formation of paramagnetic metallacarbene derivatives.

Research has been conducted on the complexation of Ln(III) ions by the meso-octaethylporphyrinogen. Isolation and structural characterization of Ln-porphyrinogen complexes are described.

The bonding between d2-vanadium(III) and calix[4] arene oxosurface was presented. It was shown that the reaction between the two compounds results to a dimer, in which vanadium(III) attains pentacoordination, when a coordinating solvent is absent. Extension of the Huckel analysis reveals that vanadium diazomethane bonding can be attained through three main orbital interactions which illustrate the high bond order of the vanadium-nitrogen bond.

Research was conducted to examine the reduction chemistry of the parent compound (cis-Cl2W(p-Bu(super t)-calix(4)-(O)4)) to generate reactive fragments such as neutral 2-W(IV)- and monoanionic d3-W(III)-tetraoxo species. The stepwise reductive coupling resulted to the formation of metal-metal-bonded metalla-calix(4)arene dimers containing double, triple and quadruple W-W bonds. To demonstrate the electronic configuration of the metal-metal functionalities when sandwiched by two calix(4)arene tetraanions, extended Huckel calculations were carried out.

The reduction-oxidation behavior of the meso-octaethyl mono(pyridine)-tris(pyrrole) macrocycle leading to C-C bonds was investigated. Lithium and the nickelII-lithium derivatives were used as model compounds to analyze the intra- and intermolecular oxidative coupling of nickel(II)-meso-octaethyl mono(pyridine)-tris(pyrrole) complex. Experimental results showed that the oxidative transformation of oligomeric porphyrinogen derivatives causes either inter- or intramolecular C-C bonding in the absence of protons.

Electrochemical, theoretical and magnetic investigation of a dinitrogen molecule bridging two vanadium centers through a controlled stepwise chemical and electrochemical reduction found that the metal center of the parent compound reacts with N2 by either oligomerizing or binding. Adding a single electron to the fourth compound induces the dimettalic unit to promote a multielectric reduction of dinitrogen in subsequent compounds. Magnetic and theoretical data indicate coupling in compounds 4,7 and 8 and the effective reduction of the dinitrogen molecule.

The role of calix(4)arene as a supporting ligand compared to cyclopentadienyl and phenoxo anion is emphasized through the micratory insertion reaction of carbon monoxide and isocyanides, in the Zr-C bond. A kinetically and structurally defined stewise insertion process is reported. The reactions occur via metal-assisted C-C bond formation, resulting in a variety of carbon-metal-bonded fragmenets. Extended Huckel calculations were also performed.

The full synthesis and chemical behaviour of the Zr-C bond functionalities bonded to the Osub4 skeleton is reported. The approach is based on the synthesis and organometallic functionalization of (calix(4)-(OMe)(O)sub3ZrC1)sub2 and (calix(4)-(OMe)sub2(O)sub2ZrC1sub2), giving rise to two classes of derivatives linked by the based-induced demethylation of a methoxy group. The main differences between the (Osub4ZR)super2+, (Osub4Zr)+ and (Cpsub2Zr)super2 fragements are emphasized.

Chemical research shows that copper(I) complexes containing pi-delocalized bidentate N-O monoanionic ligands can be designed as efficient photosensitizers in the transformation of norbornadiene into quadricyclene. Evidence suggests that the complexes are effective because they contain metal-to-ligand charge-transfer bands.

A study was conducted on the storage of electrons in the formation of the most common C-C bonds as well as the generation of electron-rich manganese(II)-Schiff base complexes and their redox chemistry. The findings led to the discovery of a novel mode of storing and releasing electrons based on reductive coupling and oxidative decoupling of C-C bonds across two Schiff base ligands.

Synthesis of the parent compound [Mn(acac-L-en)]2 [L = CH2CH2], was performed via a metathesis reaction from MnCl2 under anhydrous and anaerobic conditions. High yield was produced through the organometallic pathway. Analysis of selected bond distances and angles for the complexes showed that the planarity of the N2O2 core in [Mn(acac-L-en)]2 [L = CH2CH2] disappeared. The coordination polyhedron possessed more similarities with a trigonal bipyramid.

Formation of carbon-carbon bonds which function as electron shuttles for the metal in the complex (Co2(MeOsalophen)2Na2(THF)4), as shown by its reaction with electrophiles such as alkyl halides and carbon dioxide, was the result of the reduction of substituted (Co(salophen)) with sodium at the metal. For salophen derivatives, the reductive coupling of imino groups was noted. These results affirm that reduction of cobalt(II)-Schiff base complexes occur at the metal, not at the ligand, even if the metal reacts as if it was in a reduced form.

The thermally- and solvent-assisted intra- and intermolecular migrations of Zr-C functionalities in dialkyl(dibenzotetramethyltetraazannulene)zirconium(IV) were investigated through experimental procedures and by means an extended Huckel analysis. It was found that Cr and the Z has different levels of reactivity, resulting in significant differences in their orbital structures.

Insertion reactions use Fe2Mes4, where Mes = 2,4,6-Me3C6H2, to prepare iron-aryl complexes with doubly functionalized or differentially functionalized iron-carbon bonds. Experimental studies reveal different reactivities for bridging and terminal mesityl with respect to migratory aptitude, enabling stepwise insertion reactions. Magnetic susceptibility studies of these dimeric iron(II) complexes at different temperatures help differentiate between antiferromagnetic couplings and the presence of a metal-metal bond and X-ray studies help characterize the various products.

Ab initio calculations of dinuclear-dinitrogen complexes help examine the energetics and mechanism of dinuclear nitrogen activation by vanadium(II) and vanadium(III) and compare mononuclear and dinuclear activation. Dinitrogen activation depends on the presence of an alkali atom, total charge and spin multiplicity of the considered state, and ranges from poor to strong in dinuclear complexes. Dinitrogen activation in mononuclear complexes is always negligible.

Two alkyl groups occupy the meso position of the porphyrinogen skeleton to produce a new oxidized form of porphyrinogen in oxidation reactions. This novel oxidation reaction involves cleavage of a cyclopropane unit formed in the reaction process. Two monoelectronic redox steps are observed in the cleavage of cyclopropane associated with the oxidation of a copper complex. An intermolecular metal-ligand redox relationship is observed in the formation of meso-octaethyl porphyrinogen-Cu(III) complex.

Redox chemistry analysis of meso-octaethylporphyrinogen-iron(II) and -cobalt(II) complexes reveals the involvement of a four-electron oxidation of porphyrinogen, leading to a novel oxidized complex form. A number of intermediates are isolated which imply a step-wise oxidation mechanism. All these oxidation processes involve the formation and subsequent cleavage of two cyclopropane units.

Titanium tetrachloride reacts with hexamethyl benzene in chlorinated solvents to give a d0-arene complex. But-2-yne is cyclotrimerized by TiCl4-promoted (eta6-C6Me6)(TiCl3)(+) complex, exhibiting the stability of the complex. A charge transfer intermediate is observed by 1H nuclear magnetic resonance spectroscopy. X-ray analysis shows these complexes to have a metallic fragment (TiCl3)(+)eta6 binding the arene moiety.

The deprotonation of tmtaaH2 through LiBu(super n) or LiMe yielded the lithium derivative (tmtaa)2Li4(DME)3. The structure of the lithium derivative consists of asymmetric units with two independent (tmtaa)Li2(DME) units linked by a third DME molecule resulting in a square pyramidal coordination. The derivative is also the starting material for the synthesis of tmtaa complexes of transition metals in inorganic solvents. The complexes (tmtaa Ti Cl2).C6H6, (tmtaa Zr Cl2).2THF and (tmtaa Hf Cl2).2THF exhibit the cis arrangement of the two functionalizable M-Cl bonds.

The first of the two methods of preparing (V acac Cl2 THF 2) involves the reductive deoxochlorination of (VO acac 2) using TiCl3(THF)3. This procedure is applicable in cases wherein the oxovanadium complex can be obtained from air-aqueous solutions. Otherwise, the second method, which involves the addition of acacNa to a solution of VCl3(THF)3, can be used. Moreover, metallic zinc can be utilized to reduce the vanadium(III) chloride intermediate to (V acac Cl THF 3).

The addition of lithiated tmtaaH2 to a solution of VCl3(THF)3 results in the synthesis of (V tmtaa Cl) which serves as a source for vanadium complexes with lower oxidation states. Subsequent introduction of Grignard reagents leads to the alkylation of the vanadium derivative to (V tmtaa R) compounds, wherein R represents Me, Ch2Ph, Ph and 2,4,6-Me3C6H2. Similarly, the metal-oxo (VO tmtaa) can also act as starting material for the preparation of organometallic derivatives. The structural conformations of (V tmtaa Cl), (V tmtaa Ph) and (V tmtaa 2,4,6-Me3C6H2) are examined using X-ray analysis and H NMR spectroscopy.

The metallation of protic dinucleating ligands, acacenH2(N,N'-ethylenebis (acetylacetone imine)), salophenH2(N,N'-o-phenylenebis(salicylaldimine)), and o-pthalic acid with homoleptic copper(I)-aryl(Cu5Mes5) compound gives dinuclear copper(I) complexes. The tetradentate ligands form a trans geometry around the copper atom. The use of toluene as a solvent and CO, PPh3, and t-BuNC as auxiliary ligands stabilise the Cu(I) ion and enhances the solubility of the resulting complexes. Thus the disproportionation of copper(I) is prevented.

The preparation of cylindrical nanostructures from the reaction of a tripodal ligand containing terminal 2,3-dihydroxypyridine groups with (arene)ruthenium(II) complex is described. The complexes form a molecular cylinder with two terminal (arene)ruthenium trimers, which act as the connecting end groups for two ligands.

The synthesis and structural characterization of samarium-dinitrogen complex is described. The chemical and geometrical peculiarities of the electron rich environment provided by the calyx[4]arene dianion is expected to disfavor any low oxidation state of a metal.

Oxygen-17 NMR spectroscopy is used to study the water exchange on Ru(CO)(H2O)(sub 5)(super 2+) and cis-Ru(CO)(sub 2)(H2O)(sub 4)(super 2+) as a function of the temperature, and on fac-Ru(CO)(sub 3)(H2O)(sub 3)(super 2+) as a function of the acid concentration. X-ray crystal structures of Ru(CO)(H2O)(sub 5)(super 2+) and cis-Ru(CO)(sub 2)(H2O)(sub 4)(super 2+) are determined and a comparison of different ground-state properties with the observed reactivities is made.