Rhodium−Hydrido−Benzylamine−Triphenylphosphine Complexes: Solid-State and Solution Structures and Implications in Catalyzed Imine Hydrogenation

The complexes cis,trans,cis-[Rh(H)2(PPh3)2(NH2CH2Ph)2]PF6 (1) and cis-[Rh(PPh3)2(NH2CH2Ph)2]PF6 (2) are characterized by X-ray crystallography; the structures are maintained in CH2Cl2 where the species are in equilibrium under H2. In MeOH and in acetone, loss of amine and/or H2 can occur. Traces of 1 and 2 are present after a Rh-catalyzed H2-hydrogenation of PhCHNCH2Ph 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.