Date of Award
Doctor of Philosophy
Craig E. Barnes, Frank Vogt, Engin H. Serpersu
Early transition metal compounds and their reactions have been widely used in catalysis and preparation of advanced materials such as metal oxides in microelectronic devices. Studies of the compounds and their reactions provide a fundamental understanding of chemistry of the compounds and are critical to their applications. This dissertation focuses on the following areas: (a) Reactions of Group 4 amide guanidinates with dioxygen or water; (b) Formation of a tantalum imide complex through an unusual α [alpha]-SiMe3 [trimethylsilyl] abstraction. Reactions of the amide guanidinates with either dioxygen or water yield products that are identified to be dimers and polymers of guanidinate oxo complexes based on NMR, IR and MS characterization. Reaction of (Me2N)2Zr[iPrNC(NMe2)NiPr]2 [diamidozirconium diguanidinate] with 1.0 atm dioxygen at 80-105 oC [degree Celsius] follows pseudo first-order kinetics: ΔH≠ [activation enthalpy] = 8.7(1.1) kcal/mol; ΔS≠ [activation entropy] = -54(3) eu; ΔG≠ 358K [activation free energy] = 28(2) kcal/mol. Addition of a radical initiator, 2,2’-azobis(2-methylpropionitrile), increases the reaction rate by almost six times. Zr(NMe2)2[iPrNC(NMe2)NiPr]2 and carbon tetrachloride undergo an amidechloride exchange, giving Zr(Cl)(NMe2)[iPrNC(NMe2)NiPr]2 [amidochlorozirconium diguanidinate] and ZrCl2[iPrNC(NMe2)NiPr]2 [dichlorozirconium diguanidinate]. Zr(Cl)(NMe2)[iPrNC(NMe2)NiPr]2 has also been prepared from the reaction of ZrCl(NMe2)3 [zirconium chloro triamide] with 2 equiv of diisopropyl carbodiimide. Ta(NMe2)4[N(SiMe3)2] [tantalum amide] has been found to undergo unusual elimination of Me3Si-NMe2 [(trimethylsilyl)dimethylamine], converting the N(SiMe3)2 [bis(trimethylsilyl)amido] ligand to the =NSiMe3 [trimethylsilylimido] ligand in [Ta(NMe2)3(=NSiMe3)]2 [hexakis(dimethylamido)bis(µ-trimethylsilylimido)]ditantalum]. The α-SiMe3 abstraction at 70–110 oC to give the imide follows first–order kinetics giving the activation parameters: ΔH≠ = 21.3(1.0) kcal/mol; ΔS≠ = -17(2) eu; ΔG≠ 343K = 27(2) kcal/mol. Crystal structure of the imide dimer is discussed.
Sharma, Bhavna, "Syntheses, Characterization and Reactions of Early Transition Metal Guanidinate and Imide Compounds. " PhD diss., University of Tennessee, 2013.