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).