Abstract
Reaction of Pd(dba)(2) and P(OPh)(3) shows a unique equilibrium where the Pd[P(OPh)(3)](3) complex is favored over both Pd(dba)[P(OPh)(3)](2) and Pd[P(OPh)(3)](4) complexes at room temperature. At a lower temperature, Pd[P(OPh)(3)](4) becomes the most abundant complex in solution. X-ray studies of Pd[P(OPh)(3)](3) and Pd(dba)[P(OPh)(3)](2) complexes show that both complexes have a trigonal geometry with a Pd-P distance of 2.25 Å due to the π-acidity of the phosphite ligand. In solution, pure Pd(dba)[P(OPh)(3)](2) complex equilibrates to the favored Pd[P(OPh)(3)](3) complex, which is the most stable complex of those studied, and also forms the most active catalytic species. This catalyst precursor dissociates one ligand to give the reactive Pd[P(OPh)(3)](2), which performs an oxidative addition of nonmanipulated allyl alcohol to generate the π-allyl-Pd[P(OPh)(3)](2) intermediate according to ESI-MS studies.