Equilibria between Palladium(II) Acetate and Olefins in Acetic Acid containing Sodium Acetate

Abstract

π-Complex equilibria between dimeric Pd(II) acetate and various olefins (ethylene, styrene, 3,3-dimethyl-1-butene, vinylic and allylic esters) in acetic acid solvent have been investigated by spectral means. The results indicate two π-complexes are formed. The first π-complex, which is formed rapidly, is a dimeric π-complex (ol = olefin ).[Formula: see text]The Benesi–Hildebrand plots for these complexes are linear for all olefins and thus values of Kπ22 can be readily evaluated. The values of the equilibrium coefficient, Kπ22, do not change with solution composition or [NaOAc]. The second π-complex is formed slowly. The data are consistent only with the equilibrium[Formula: see text]The data are inconsistent with the equilibrium[Formula: see text]which is analogous to that reported for the Na2Pd2Cl6 reaction with olefins in acetic acid. Furthermore, previous assumptions as to the equilibria between ethylene and Pd(II) in the all-acetate system have proved incorrect, and so the kinetics of oxidation of ethylene in this system must be reinterpreted in view of the present results.