Reaction of Coordinated Phosphines. IV. Mechanism of Carbon-Phosphorus Bond Cleavage in Triarylphosphines and Trialkylphosphines by Palladium(II) Acetate

Reaction of triphenylphosphine with an equimolar amount of Pd(OAc)2 in acetic acid at room temperature in the presence of styrene gave trans-stilbene(94%), H3PO4(0.8%), PhP(O)(OH)2(40%), Ph2P(O)(OH)(19%), and Ph3P=O(35%). Reactions of tributyl- and trioctylphosphine with Pd(OAc)2 in acetic acid at 90 °C yielded butene(20%) and octene(1-; 22%, 2-; 17%), respectively, as main products. The phenylation of some olefins with triphenylphosphine in acetic acid-d, as well as other features of the reaction lead to the conclusion that nucleophilic attack on coordinated phosphorus atom is the most probable pathway for the formation of the phenylation agent (phenylpalladium species) in the reaction system among the others, ortho-metallation and oxidative addition.