Reactions of cyclopalladated complexes with HPPh2 resulting in ligand phosphination

Abstract

Reactions of a dinuclear chloro-bridged cyclopalladated complex (CPC) derived from N,N-dimethylbenzylamine with HPPh2 under a variety of conditions resulted in the phosphination of the cyclopalladated ligand. The best yield (77%) of the reaction product, ortho-(diphenylphosphino)-N,N-dimethylbenzylamine, was achieved using 4.5 equiv. of HPPh2 in toluene in the presence of Cs2CO3 at 40 °C. The scope of the reaction was explored with a range of enantiopure and achiral C,N, C,S and C,P CPCs having either five- or six-membered rings and containing either an sp2 or sp3CPd bond. The corresponding N,P, S,P, and P,P ligands or their oxides were isolated in 30–70% yields. Reactions of HPPh2 in toluene with CPCs derived from D-camphor methyloxime and 2-tert-butyl-4,4-dimethyl-2-oxazoline provided unique mononuclear Pd(II) complexes with a terminal PPh2 ligand in 16 and 52% yield, respectively. Structures of all new compounds were supported by 1H, 13C{1H}, DEPT, 31P{1H}, and 2D NMR spectra.