Rhodium(III)-NSi Catalyzed Styrene Hydrosilylation: Evidence of the Hemilabile Character of NSi-Type Ligands

The 18e saturated rhodium(III) species [Rh(H)(X)(κ²-NSi^tBu2)(bipy^Me2)] (NSi^tBu2={4-methylpyridine-2-yloxy}ditertbutylsilyl; bipy^Me2=4,4'-dimethylbipyridine) (X=Cl, 1; OTf, 2) have been prepared and characterized by NMR spectroscopy and in the case of 2 it has been possible to determine its solid-state structure by X-ray diffraction. Complex 1 has proven to be an effective catalyst precursor for the reaction of styrene derivatives with hydrosilanes in CD₂Cl₂. However, under catalytic conditions complex 2 decomposes. The performance of the 1-catalyzed reaction of styrene with hydrosilanes strongly depends on the nature of the silane, the best catalytic performance was achieved using HSiMe₂Ph. Theoretical and ¹H NMR studies indicate that the hemilabile nature of the NSi ligand is key to understanding the catalytic activity of compound 1.