Hydrosilylation and Silane Polymerization Catalyzed by Group 4 Amidometallocene Cations

Four cationic amidotitanocene complexes [Cp2Ti(NRR′)][B(C6F5)4] (Cp = η5-C5H5; 1a: R = R′ = p-anisyl; 1b: R = p-fluorophenyl, R′ = p-anisyl; 1c: R = p-fluorophenyl, R′ = phenyl; 1d: R = phenyl, R′ = 2-pyridyl) were synthesized. Complexes 1a–d undergo Ti–N bond homolysis under visible light irradiation. Complexes 1a–c catalyze the polymerization of phenylsilane to yield branched polysilane polymers with molecular weights (Mw) up to approximately 3000 and dispersity indexes (Đ) of 1.4–1.6. Previously reported Group 4 cationic amidometallocene complexes [Cp2Ti(NPh2)][B(C6F5)4] (Ia) and Cp2Zr(NPh2)][MeB(C6F5)3] (IIa) were also tested in the hydrosilylation of carbonyl compounds with triethylsilane (Et3SiH). In some cases, complex Ia afforded completely reduced products (e.g., ethylbenzene from acetophenone), while IIa was generally more selective (e.g., (1-phenylethoxy)triethylsilane from acetophenone) but also more active. Complex IIa could also convert anisole derivatives to phenoxysilanes with high efficiency (TON = 2000).