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.