Silyl derivatives of [Bis(8-quinolyl)methylsilyl]iridium(III) complexes: Catalytic redistribution of arylsilanes and dehydrogenative arene silylation

The reactive complex (NSiN)Ir(H)(OTf)(coe) (1; NSiN = bis(8-quinolyl) methylsilyl, coe = cyclooctene) was generated by reaction of the previously reported (NSiN)Ir(H)Cl(coe) with 1 equiv of AgOTf. Addition of Ph ₃SiH to 1 in benzene led to Si-H bond activation and octane elimination with formation of the α-Ph-migrated, 16-electron product (NSiN)IrPh(SiPh ₂OTf) (2). The ²⁹Si{ ¹H} NMR resonance of 2 at δ 54.0 indicates iridium silyl character, and X-ray crystallography reveals the presence of a highly distorted triflatosilyl group. In acetonitrile, 1 reacts with various silanes to give stable, cationic Ir(III) complexes of the type [(NSiN)IrSiR ₃(NCMe) ₂][OTf] (R = OSiMe ₃, Et, Ph) or [(NSiN)Ir{SiH(R)Ph)(NCMe) ₂][OTf] (R = H, Ph) in good yields. Complex 1 is an active catalyst for arylsilane redistribution and for the dehydrogenative silylation of arenes. The cationic, THF complex [(NSiN)Ir(H)(coe)(THF)] [B(C ₆F ₅) ₄] (10), a product of the reaction of 1 with 1 equiv of Li(Et ₂O) ₃[B(C ₆F ₅) ₄] in THF, is a slower catalyst for silane redistribution and dehydrogenative arene silylation. A series of new iridium phosphine complexes were prepared, including (NSiN)Ir(H)Cl(PMe ₃) (13), [(κ ²-NSiN)Ir(H)(PMe ₃) ₃][Cl] (14), and (κ ¹-NSiN)Ir(H)(Me) (PMe ₃) ₃ (15). Treatment of the previously prepared (NSiN)Ir(H)Cl(PPh ₃) with 1 equiv of LiBEt ₃H afforded the dihydride complex (NSiN)IrH ₂(PPh ₃) (11), which features a hydride ligand in a coordination site trans to the NSiN silyl group. The triflate complex (NSiN)Ir(H)(OTf)(PPh ₃) (16) was obtained by reaction of (NSiN)Ir(H)Cl(PPh ₃) with 1 equiv of AgOTf in dichloromethane or by reaction of 1 with 1 equiv of PPh ₃ in dichloromethane.