Reactions of Cationic PNP-Supported Iridium Silylene Complexes with Polar Organic Substrates

Reactions of PNP-supported silylene complexes [(PNP)(H)Ir=SiRR'[B(C6F5)(4)] (R = R' = Ph (I) and R = H, R' = Mes (2)) with Lewis bases, carbonyl compounds, alcohols, and amines were investigated. Addition of DMAP (4-dimethylaminopyridine) to 1 and 2 produced base-stabilized silylene complexes [(PNP)(H)IrSiRR'(DMAP)][B(C6H5)(4)](R = R' = Ph (3) and R = H, R' = Mes (4)). Reactions of 2 with benzophenone and benzaldehyde afforded the products of stoichiometric hydrosilylation, heteroatomsubstituted silylene complexes [(PNP)(H)Ir=SiMes(OCH(Ph)(R))][B(C6F5)(4)] (R = Ph (5) and R = H (6)). Complex 1 reacted with DM F or benzophenone, and 2 reacted with DMF, to afford base-stabilized silylene complexes of the type [(PNP)(H)IrSiRR'(B)][B(C6F5)4] (R = H, R' = Mes, B = DM F (7); R = R' = Ph, B = DMF (8) and O=CPh2 (9)). In contrast, treatment of I with acetophenone afforded {(PNPH)IrH[SiPh2(OC(=CH2)Ph)]}[B(C6F5)(4)] (10), from activation of a C H bond at the a-carbon position of acetophenone. Reactions of alcohols and amines with 1 afforded [(PNPH)IrH(SiPh,OR)][B(C6F5)4] (R = 3,5-(Bu2C6H3)-Bu-t (II), R = Ph (12), R = Pr-t (13), and R = Bu-t (14)) and [(PNPH)IrH(SiPh2NHR)][B(C6F5)(4)] (R = Ph (15), R = 3,5-(CF3)(2)C6H3 (16)). Exploration of the catalytic activity of iridium silylene complexes with these organic substrates demonstrated that 1 is an effective catalyst for silane alcoholysis and aminolysis and for the hydrosilylation of ketones.