Syntheses and Reactions of Early Transition Metal Amidinate Compounds

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Lamb, Adam Christopher
Amidinate; Peroxo; Zirconium; Tantalum; Amide; Niobium; Inorganic Chemistry
thesis / dissertation description
Homoleptic Groups 4 and 5 metal amide compounds have been used as precursors in CVD/ALD processes to make microelectronic metal oxide thin films. These compounds are often very air sensitive. Ancillary ligands such as amidinates have been used to reduce their air sensitivity and to make their handling easier. Reactions of amidinates with dioxygen and water have thus been used to make metal oxide thin films. Studies of these reactions are important in order to make better precursors and purer thin films. This dissertation focuses on the following areas: (a) Syntheses of zirconium and Group 5 amidinate amides; (b) Studies of the reactions of zirconium amidinate amides with dioxygen or water; (c) Probing the pathway in the formation of an archetypical tungsten alkylidyne complex. Zr[MeC(NiPr)2]2(NMe2)2 [zirconium amidinate amide] has been prepared through three different routes: two salt metathesis reactions and one aminolysis. The aminolysis of M(NR2)n [metal amide] with iPrN(H)C(Me)=NiPr [diisopropylamidine] gives cleaner products in better yields and this route has been chosen to make amidinates in this dissertation. Reactions of zirconium amidinate amide complexes with dioxygen, water or hydrogen peroxide have been studied. Metal-containing products were {(µ-O)Zr[MeC(NiPr)2]2}2 [zirconium amidinate oxo dimer] and {(µ-O)Zr[MeC(NiPr)2]2}n [zirconium amidinate oxo polymer] based on NMR, IR, MS and elemental analysis. Also, the reaction of Zr[MeC(NiPr)2]2(NMe2)2 with dioxygen yields {(m-h2:h2-O2)Zr[MeC(NiPr)2]2}3 [zirconium peroxo amidinate trimer] and its crystal structure is reported. Ta[MeC(NiPr)2](NMe2)4 [tantalum amidinate amide] and carbon tetrachloride undergo an amide-chloride exchange, giving Ta[MeC(NiPr)2](NMe2)3Cl [tantalum amidinate amide chloride]. Ta[MeC(NiPr)2](NMe2)3Cl has also been synthesized through the aminolysis of Ta(NMe2)4Cl [tantalum amide chloride] with a diisopropyl amidine. W(CH2tBu)3(≡CtBu) [tungsten neopentyl neopentylidyne] has been prepared through the reaction of W(OMe)3Cl3 [tungsten chloride methoxide] and Zn(CH2tBu)2 [dineopentyl zinc]. Also, a side product which has been characterized through NMR spectroscopies to be W(OMe)2Cl(CH2tBu)3 [tungsten neopentyl chloride methoxide].