 As in the case with the metal carbonyl catalysts, bulky secondary amine-boranes form monomeric aminoboranes.For RhL2- and Rh(H)2L2-derived catalysts, the active species is a homogeneous catalyst, with the phosphine ligands interacting directly with the dehydrocoupling process.Changing the phosphine ligands from P"i"Pr3 to P"i"Bu3 significantly increases the turnover rate of the catalyst.