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 Ph3SiH 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(SiPh2OTf) (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)IrSiR3(NCMe)2][OTf] (R = OSiMe3, 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(C6F5)4] (10), a product of the reaction of 1 with 1 equiv of Li(Et2O)3[B(C6F5)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(PMe3) (13), [(κ2-NSiN)Ir(H)(PMe3)3][Cl] (14), and (κ1-NSiN)Ir(H)(Me)(PMe3)3 (15). Treatment of the previously prepared (NSiN)Ir(H)Cl(PPh3) with 1 equiv of LiBEt3H afforded the dihydride complex (NSiN)IrH2(PPh3) (11), which features a hydride ligand in a coordination site trans to the NSiN silyl group. The triflate complex (NSiN)Ir(H)(OTf)(PPh3) (16) was obtained by reaction of (NSiN)Ir(H)Cl(PPh3) with 1 equiv of AgOTf in dichloromethane or by reaction of 1 with 1 equiv of PPh3 in dichloromethane.