Synthesis and Reactions of and Catalytic Homogeneous Hydrogenation by Chlorocarbonyl(o-(diphenylphosphino)-N,N-dimethylaniline)iridium(I) and chlorocarbonyl(o-(diphenylphosphino)-N,N-dimethylbenzylamine)iridium(I)

Complexes IrCl(CO)PN and IrCl(CO)PCN, where PN is o-(diphenylphosphino)-N,N-dimethylaniline and PCN is o-(diphenylphosphino)-N,N-dimethylbenzylamine, have been prepared. The compounds react with HCl and with a mixture of MeI and iodide to give IrHCl₂(CO)PN, IrHCl₂(CO)PCN, IrMeI₂(CO)PN, and IrMeI₂(CO)PCN. The relative order of effectiveness for the catalytic hydrogenation of hexene-1 is IrCl(CO)PCN > IrCl(CO)PN > IrCl(CO)(PPh₃)₂. The compound IrCl(CO)PCN is conformationally mobile because of inversion of the six-membered ring. Values for E_a, ΔH^‡, and ΔS^‡ are 18.0 kcal/mol, 17.5 kcal/mol, and 15.3 cal/(deg mol), respectively, which compare to values of 8.8 kcal/mol, 8.3 kcal/mol, and -17.4 cal/(deg mol) for RhCl(CO)PCN. Equilibrium measurements of [Ir(III)]/[Ir(I)] for the addition of benzoic acid to IrCl(CO)PCN, IrCl(CO)PN, and IrCl(CO)(PPh₃)₂ show that there is little difference in the basicities of the three metal centers. The compounds IrCl(CO)(PCN)₂ and IrCl(CO)(PO)₂ are also described, where PO is o-(diphenylphosphino)anisole.