MECHANISM OF THE FORMATION OF PALLADIUM COMPLEXES SERVING AS CATALYSTS ON HYDROGENATION REACTIONS. I. REACTIONS OF COMPLEXES WITH MOLECULAR HYDROGEN

Article abstract of DOI:10.1016/S0022-328X(00)85857-X

The interaction of 2 with molecular H2 yields a binuclear complex of zero-valent palladium, (Ph3P)2Pd2.This complex interacts reversibly with H2 in CH2Cl2, yielding (Ph3P)2Pd2H2.In argon atmosphere (Ph3P)2Pd2 reacts with 2 to form a binuclear complex of Pd^I with a metal-metal bond.These data, as well as the results of kinetic studies of the reactions between 2 and H2, are in agreement with an autocatalytic mechanism for the process, including catalysis of the reduction of Pd^II complexes by the Pd⁰ compounds.It has been established that the synthesized compounds of Pd^II, Pd^I and Pd⁰ with the ratio P/Pd<*>1, are inactive in the hydrogeneration of unsaturated compounds.The catalytically active complex (PPh)2Pd5 is formed when palladium acetate reacts with (Ph3P)2Pd2 in the presence of H2.The same compound is formed when a solution of (Ph3P)2Pd2 is treated with a mixture of H2 and O2 (or H2O2 in an atmosphere of H2). (PPh)2Pd5 is an effective catalyst for the hydrogenation of olefins, dienes, acetylenes, aldehydes, organic peroxides, quinones, O2, Schiff bases, and nitro, nitroso, and azo compounds.