Rhodium-hydrido-benzylamine-triphenylphosphine complexes: solid-state and solution structures and implications in catalyzed imine hydrogenation

The complexes cis,trans,cis-Rh(H)(2)(PPh(3))(2)(NH(2)CH(2)Ph)(2)]PF(6) (1) and cis-Rh(PPh(3))(2)(NH(2)CH(2)Ph)(2)]PF(6) (2) are characterized by X-ray crystallography; the structures are maintained in CH(2)Cl(2) where the species are in equilibrium under H(2). In MeOH and in acetone, loss of amine and/or H(2) can occur. Traces of 1 and 2 are present after a Rh-catalyzed H(2)-hydrogenation of PhCH=NCH(2)Ph in MeOH, where the amine is generated by hydrolysis of the imine substrate through adventitious water. The findings are relevant to catalyst poisoning in the catalytic process.