A highly efficient, practical, and general route for the synthesis of (R3P)2Pd(0): structural evidence on the reduction mechanism of Pd(II) to Pd(0).

A highly efficient, practical, and general method was developed to synthesize a family of (R(3)P)(2)Pd(0) complexes, using a stoichiometric amount of phosphine ligands and readily available Pd(II) precursors. The stepwise pathway of reducing Pd(II) to Pd(0) was established by isolating two key intermediates. Both [t-Bu(2)(4-Me(2)NC(6)H(4))P](2)Pd and (t-Bu(2)NpP)(2)Pd are new compounds. Preliminary studies on [t-Bu(2)(4-Me(2)NC(6)H(4))P](2)Pd have indicated that it is a very active catalyst (84-95% isolated yield) in the Cu-free Sonogashira coupling involving aryl and heteroaryl chlorides at 0.5 mol % catalyst loading.