P-C-Activated Bimetallic Rhodium Xantphos Complexes: Formation and Catalytic Dehydrocoupling of Amine-Boranes

{Rh(xantphos)}-based phosphido dimers form by P-C activation of xantphos (4,5-bis(diphenylphosphino)-9,9-dimethylxanthene) in the presence of amine-boranes. These dimers are active dehydrocoupling catalysts, forming polymeric [H2BNMeH](n) from H3B center dot NMeH2 and dimeric [H2BNMe2](2) from H3B center dot NMe2H at low catalyst loadings (0.1 mol%). Mechanistic investigations support a dimeric active species, suggesting that bimetallic catalysis may be possible in amineborane dehydropolymerization.