Synthetic approaches to problems in materials science: development of novel organometallic compounds for specific applications
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The chemical vapor deposition of thin, epitaxial layers of titanium nitride for use in electronic devices is a subject of continuing research. The development of novel titanium hydrazides as single-source precursors for titanium nitride has been outlined. The molecular structures of a series of titanium hydrazides utilizing 1,1-dimethylhydrazide(-1), 1,2-diphenylhydrazide(-1), 1,2- diphenylhydrazide(-2), trimethylhydrazide and N,N’-bis(trimethylsilyl)- benzamidinate ligands are presented. By examination of the variation in structure and hydrazide ligand bonding modes from one ligand system to the next, the effects of small changes in the hydrazide substitution on overall titanium hydrazide geometry have been elucidated. In an effort to create novel olefin polymerization catalysts, the first structurally authenticated examples of p-block element complexes utilizing the “constrained geometry” ligand, [(C5Me4)(t-BuN)SiMe2] -2 (CGC), have been prepared. P-block element constrained geometry complexes show dramatic structural differences from the known d- and f-block metal complexes. Group 13 complexes (CGC)EMe·(THF) (E = Al, Ga) exhibit unprecedented η1 σ-type interactions between the group 13 element and the C5Me4 ring. The dinuclear complexes [Mg2Cl3(THF)6][GaCl3(CGC)GaCl2] and [Mg2Cl3(THF)6][InBr3(CGC)InBr2] feature an equally unprecedented bridging bonding mode for the constrained geometry ligand, and are the first unequivocal examples of η2 π-donation to a gallium(III) or indium(III) metal center, respectively. Group 15 complexes (CGC)ECl and the corresponding tetrachloroaluminate salts [(CGC)E][AlCl4] (E = P, As, Sb) undergo rearrangement of the constrained geometry ligand itself to produce entirely unpredicted complexes. The crystallographically observed molecular structures have been compared to those predicted by DFT calculations. Ethylene polymerization studies employing several of these p-block complexes have been performed.