Cross-Dehydrogenative Coupling of Secondary Amines with Silanes Catalyzed by Agostic Iridium-NSi Species

An active catalytic system for the cross-dehydrogenative coupling (CDC) of a wide range of secondary amines with silanes is reported. The iridium(III) derivatives [Ir(H)(X)(κ²-NSi^DMQ)(L)] (NSi^DMQ = {4,8-dimethylquinoline-2-yloxy}dimethylsilyl; L = coe, X = Cl, <b>2</b>; L = coe, X = OTf, <b>3</b>; L = PCy₃, X = Cl, <b>4</b>; L = PCy_3, X = OTf, <b>5</b>), which are stabilized by a weak yet noticeable Ir···H-C agostic interaction between the iridium and one of the C-H bonds of the 8-Me substituent of the NSi^DMQ ligand, have been prepared and fully characterized. These species have proven to be effective catalysts for the CDC of secondary amines with hydrosilanes. The best catalytic performance (TOF_1/2 = 79,300 h^-1) was obtained using <b>5</b> (0.25 mol %), <i>N</i>-methylaniline, and HSiMe₂Ph. The catalytic activity of the species [Ir(H)(OTf)(κ²-NSi^Q)(PCy₃)] (<b>10</b>, NSi^Q = {quinoline-2-yloxy}dimethylsilyl) and [Ir(H)(OTf)(κ²-NSi^MQ)(PCy₃)] (<b>11</b>, NSi^MQ = {4-methylquinoline-2-yloxy}dimethylsilyl), related to <b>5</b> but lacking the 8-Me substituent, is markedly lower than that found for <b>5</b>. This fact highlights the crucial role of the 8-Me substituent of the NSi^DMQ ligand in enhancing the catalytic performance of these iridium complexes.