Mechanism of the formation of palladium complexes serving as catalysts in hydrogenation reactions : I. Reactions of complexes with molecular hydrogen |
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| Authors: | AS Berenblyum AG Knizhnik SL Mund II Moiseev |
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| Institution: | All-Union Scientific Research Institute of Petroleum Processing (Elektrogorsk Branch), Elektrogorsk U.S.S.R.;Institute of General and Inorganic Chemistry, Academy of Sciences of the USSR, Moscow U.S.S.R. |
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| Abstract: | The interaction of Ph3PPD(OAc)22 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 Ph3PPd(OAc)22 to form a binuclear complex of PdI with a metal—metal bond. These data, as well as the results of kinetic studies of the reactions between Ph3PPd(OAc)22 and H2, are in agreement with an autocatalytic mechanism for the process, including catalysis of the reduction of PdII complexes by the Pd0 compounds. It has been established that the synthesized compound of PdII, PdI and Pd0 with the ratio P/Pd?1, are inactive in the hydrogenation 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. |
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