Using NMR and ESI‐MS to Probe the Mechanism of Silane Dehydrocoupling Catalyzed by Wilkinson's Catalyst

The reaction of Wilkinson's catalyst Rh(PPh 3 ) 3 Cl ( 1 ) with 1–2 equiv. of di‐ n ‐hexylsilane gives rise to a complex mixture of products, which has been analyzed by 31 P{ 1 H} NMR and shown to include the hydrido complex Rh(PPh 3 ) 3 H ( 3 ). Continuous sampling of the 1:1 reaction mixture by ESI‐MS provided time‐dependent speciation that tracks the formation of 3 at the expense of the initial silane oxidative addition product [Rh(PPh 3 ) 2 (Cl)(H){Si( n Hex) 2 H}] ( 2 ), the subsequent 1st order disappearance of 3 , and the formation of other, minor side‐products. Our results provide insight into established activity of 1 for catalytic dehydrocoupling of di‐ n ‐hexylsilane, and implicate complex 3 as the active species in this catalysis.