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

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