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 K_π22 can be readily evaluated. The values of the equilibrium coefficient, K_π22, 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.