Silyl Derivatives of [Bis(8-quinolyl)methylsilyl]iridium(III) Complexes:  Catalytic Redistribution of Arylsilanes and Dehydrogenative Arene Silylation

Abstract

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 3 SiH 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 2 OTf) ( 2 ). The 29 Si{ 1 H} 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 6 F 5 ) 4 ] ( 10 ), a product of the reaction of 1 with 1 equiv of Li(Et 2 O) 3 [B(C 6 F 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 3 H 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.