Electrophilic bis(guanidinate)titanium and bis(amidinate)tantalum complexes: Reactivity studies and solution and solid-state structural analyses

Chapter 1. The reactivity of an electronically unsaturated tantalum methylidene complex supported by [TolC(NSiMe₃)₂] ligands is described. Electrophilic addition and olefination reactions of the Ta = CH₂ functionality are reported. This complex also participates in group-transfer reactions not observed in sterically similar, but electronically saturated, analogues.; Chapter 2. The tantalum methylidene complex [TolC(NSiMe ₃)₂]₂Ta(CH₂)CH₃ reacts with pyridine N-oxides to form the tantalum oxo complex [TOlC(NSiMe₃)₂]₂Ta(O)CH₃ and methylpyridines. The methylation occurs regioselectively at the unsubstituted ortho position in each pyridine N-oxide. A mechanistic study of this reaction is presented.; Chapter 3. A titanium dinitrogen complex, {lcub}[Me ₂C(NiPr)₂Ti{rcub}₂(N₂), is synthesized by reduction of the dichloride precursor, [Me₂C(N iPr)₂]₂TiCl₂. The dinitrogen complex undergoes group-transfer reactions to yield complexes containing titanium-heteroatom bonds (Ti-X and Ti = X; X = NR, O, S). The solid-state and solution structures of the compounds are discussed. This includes variable temperature and two-dimensional NMR experiments used to observe isomerization reactions and a novel guanidinate rearrangement.; Chapter 4. The synthesis of [PhC(NSiMe₃) ₂]₂TaF₃ and its conversion to alkyl and aryl derivatives is reported. The solid-state structures of these seven-coordinate compounds were determined and compared with solution data from variable temperature NMR experiments.