This dissertation concerns the discovery of the ability of the guanidinate ligand hpp (hpp = anion of 1,3,4,6,7,8-hexahydropyrimido[1,2-a]pyrimidine) to stabilize high oxidation states of dimetal units (particularly dimolybdenum species) and attempts to control solubility and redox potential through modification of the ligand. Two general strategies were used for the ligand modifications: alteration of the ring size, and addition of alkyl substituents. All of the dimetal complexes using these ligands show a significant shift in redox potential compared to other commonly used classes of ligands (i.e. carboxylates and formamidinates) allowing access to the Mo2 4+, Mo2 5+ and Mo2 6+ oxidation states. The solubility of the complexes increases with increasing ring size, or with increasing length of the alkyl substituent. The physical and chemical properties of the ligands and their dimolybdenum complexes are described in detail.

This dissertation concerns the use of bicyclic guanidinate ligands to prepare new dimetal paddlewheel compounds. Specifically, Ru_2^6+, Re_2^6+, Re_2^7+, and Os_2^7+ compounds will be examined to observe any changes brought about by using bicyclic guanidinate ligands with varying ring sizes. In the Ru_2^6+ compounds, different ligand ring sizes cause a change in the electronic configuration and magnetic properties. Bicyclic guanidinate ligands allow the preparation of Re_2^7+ compounds from Re_2^6+ compounds, both of which are examined structurally and electrochemically. [Os2(hpp)4]^+ is examined to improve upon earlier studies, yielding a model of the g-tensor components with respect to the compound structure. An additional project included in the dissertation involves the study of an asymmetric trinickel extended metal atom chain. The structural effects of the asymmetry are examined to help elucidate the magnetic behavior that differs significantly from symmetric trinickel extended metal atom chains.

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This dissertation focuses on two different types of organometallic compounds, carbenes and imides. The first project deals with the archetypal Schrock carbene, and the second project studies complexes that contain metal-nitrogen bonds, both amides and imides. A summary of the research in this dissertation is discussed in Chapter 1. Chapter 2 begins the studies of the archetypal Schrock carbene (ButCH2)3Ta=CHBut. The studies include the synthesis of deuterated compounds (ButCD2)3TaCl2 and ButCD2Li, observation and identification of the intermediate, Ta(CD2But)5, and kinetic studies of the conversion of Ta(CD2But)5 to (ButCD2)3Ta=CDBut, giving the activation parameters and a kinetic isotope effect for the conversion. The work here confirms that the pentaneopentyltantalum is the precursor to the archetypal Schrock carbene. Chapter 3 studies the effects of isotopic substitution on NMR chemical shifts of complexes in Chapter 2. Conformations of (ButCD2)3TaCl2 and Ta(CD2But)5 have also been investigated. Chapter 4 begins the study of compounds containing metal-nitrogen bonds. Guanidinate imides Ta(NMe2)(=NSiMe3)[RNC(NMe2)NR]2 (R = Cy, Pri) have been prepared from the reactions of Ta(NMe2)4[N(SiMe3)2] with two equivalents of carbodiimides, RN=C=NR. The two guanidinate imides have been characterized by NMR spectroscopy and elemental analysis. In addition, the structure of Ta(NMe2)(=NSiMe3)[CyNC(NMe2)NCy]2 has been studied by single crystal X-ray diffraction. Under heating, Ta(NMe2)4[N(SiMe3)2] undergoes an unprecedented elimination of Me3Si-NMe2, converting the amide ligand –N(SiMe3)2 to the imide ligand =NSiMe3 to give an intermediate Ta(NMe2)3(=NSiMe3). In the presence of CyN=C=NCy, the carbodiimide captures the intermediate to give another intermediate Ta(NMe2)2(=NSiMe3)[CyNC(NMe2)NCy]. Subsequent second carbodiimide insertion leads to the formation of the final product Ta(NMe2)(=NSiMe3)[CyNC(NMe2)NCy]2. The remaining amide ligand, –NMe2, in Ta(NMe2)(=NSiMe3)[CyNC(NMe2)NCy]2 and Ta(NMe2)(=NSiMe3)[PriNC(NMe2)NPri]2 gives two separate resonances in the proton NMR spectrum at room temperature indicating inequivalence of the two methyl groups. The interconversion of the methyl groups in the former has been studied with variable-temperature NMR. Chapter 5 studies the synthesis and characterization of metal cage complexes [(Me2N)3MO]4 (M = Nb, Ta). Single crystal X-ray diffraction studies show a cubane-like structure with M-O bridges. Variable-temperature NMR of the inequivalent amide methyl groups –NMeAMeB has also been carried out to find the activation parameters for the exchange.

De nouveaux précurseurs pour LI-MOCVD (Liquid injection Metal Organic Chemical Vapor Deposition) de Hf et de Zr ont été synthétisés et caractérisés par IR-TF, RMN multinoyaux, diffraction des RX sur monocristal et par ATG. La comparaison des comportements thermiques de différents complexes synthétisés a permis d'étudier l'effet de différents groupements sur leur volatilité et leur stabilité thermique. Les mono-amidinates et les monoguanidinates sont apparus plus volatiles et moins stables thermiquement que les di-amidinates et les di-guanidinates. Les films d'oxyde d'hafnium déposés ont été caractérisés par DRX, XRR, ATR et XPS. Les mono-guanidinates asymétriques tel que Hf(NEt2)3(iPr-Et2-tBu-GUA) et les di-guanidinates asymétriques tel que Hf(NMe2)2(Et-Me2-tBu-GUA)2 sont très prometteurs pour le dépôt de couches d'HfO2. Ils permettent la stabilisation d'une phase d'HfO2 de structure cristalline de symétrie supérieur à la phase monoclinique à 580°C. De plus, ces précurseurs permettent l'obtention des films de HfO2 nitruré en absence d'une étape supplémentaire de nitruration