Cationic amidotitanocene complexes [Cp2Ti(NPhAr)][B(C6F5)4] (Cp=η5‐C5H5; Ar=phenyl (1 a), p‐tolyl (1 b), p‐anisyl (1 c)) were isolated. The bonding situation was studied by DFT (Density Functional Theory) using EDA‐NOCV (Energy Decomposition Analysis with Natural Orbitals for Chemical Valence). The polar Ti−N bond in 1 a–c features an unusual inversion of σ and π bond strengths responsible for the balance between stability and reactivity in these coordinatively unsaturated species. In solution, 1 a–c undergo photolytic Ti−N cleavage to release Ti(III) species and aminyl radicals ⋅NPhAr. Reaction of 1 b with H3BNHMe2 results in fast homolytic Ti−N cleavage to give [Cp2Ti(H3BNHMe2)][B(C6F5)4] (3). 1 a–c are highly active precatalysts in olefin hydrogenation and silanes/amines cross‐dehydrogenative coupling, whilst 3 efficiently catalyzes amine‐borane dehydrogenation. The mechanism of olefin hydrogenation was studied by DFT and the cooperative H2 activation key step was disclosed using the Activation Strain Model (ASM).
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).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.