Kinetics of the carbomethoxylation of methylacetylene-allene mixtures catalyzed by palladium complexes

Pathways leading to the desired product and by-product (copolymer of allene and CO) were determined for the carbomethoxylation of allene—methylacetylene mixtures catalyzed by the PdCl₂(Ph₃P)₂—HCl—ortho—phenanthroline system. Ratios for the rates of these transformations were found. Allene methylacetylene isomerization under carbomethoxylation conditions was observed.Translated from Kinetika i Kataliz, Vol. 46, No. 1, 2005, pp. 50–53.Original Russian Text Copyright © 2005 by Korneeva, Karaskova, Makarov, Slivinskii.     

Mechanism of the formation of palladium complexes serving as catalysts in hydrogenation reactions : I. Reactions of complexes with molecular hydrogen

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 Pd^I 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 Pd^II complexes by the Pd⁰ compounds. It has been established that the synthesized compound of Pd^II, Pd^I 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.     

Mechanism of the formation of palladium complexes serving as catalysts in hydrogenation reactions : II. Reactivity of palladium phosphine halides towards molecular hydrogen

[(PPh₃)₃(PPh₂)₂Pd₃Cl] Cl, benzene and aniline hydrochloride were isolated as products of the reactions of (PPh₃)₂PdCl₂]₂ or [(PPh₃)PdCl₂]₂ with H₂ in organic amines (Am). Similar products were obtained when (Ph₃P)₂Pd(Ph)Br was treated with H2₃ Both in amines and aromatic solvents. The reaction between H₂ and [(PBu₃)PdCl₂]₂ resulted in the formation of [(PBu₃(PBu_2)PdCl2 ·. 2 Am The kinetic data for H₂ absorption by solutions of palladium(II) complexes are consistent with the heterolytic mechanism of cleavage fo hte HH bond in the coordination sphere of palladium(II); the function of the H⁺ acceptor being performed by the bases (e.g. Am or Ph). The reaction between the palladium complexes and H₂ is autocatalytic. Reduction of the initial Pd^II complexes leads to lower oxidation state palladium complexes, which catalyse the reduction of Pd^II complexes. In the coordination sphere of the lower oxidation state palladium complexes, the oxidative addition of PR₃ to Pd takes place with formation of compounds containing a Pd-R bond. It is the reaction between these complexes and H₂ that yields palladium compounds with PR₂ ligands.     

Activation of molecular hydrogen by transition-metal complexes. 2. Formation of complexes,of palladium (O) and (+1) with a metal-metal bond during hydrogenolysis of [Ph3PPd(OAc)2]2

Conclusions The reaction of dipalladium -diacetatediacetatoditriphenylphosphine [Ph₃PPd(OAc)₂]₂ with hydrogen leads to formation of complexes of Pd(0), (Ph₃P)₂Pd₂, and of Pd(+l), (Ph₃PPd(OAc)₂, with a metal-metal bond.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1687–1690, August, 1979.     

Kinetics of homogeneous hydrogenation of cyclohexene catalyzed by complexes of rhodium and iridium with a terdentate ligand

Complexes of the composition MC1HN (CH₂CH₂AsPh₂)₂ (M= =Rh(I), Ir(I) were used as catalysts for the homogeneous hydrogenation of cyclohexene over the temperature range 20–50 °C and 0.4 to 1 atm hydrogen partial pressure. The dependence of rate of hydrogenation on temperature, hydrogen concentration, catalyst concentration and substrate concentration is reported. The activation parameters of the reaction, H* and S* have been evaluated.

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MC1HN (CH₂CH₂AsPh₂)₂ (M=Rh(I) Ir(I) 20–50°C 0,4 1 atm. , , . H^* S^*.

     

Ester hydrogenation catalyzed by Ru-CNN pincer complexes

We report new Ru-CNN pincer catalysts for ester hydrogenation under mild conditions.     

纳米多孔钯催化亚胺化合物加氢还原反应研究

本文首次研究了以H2为氢源、纳米多孔钯催化亚胺化合物的加氢还原反应.结果表明:在氢气压力为101.325 kPa,溶剂为无水乙醇,反应温度为30℃,反应时间24 h,催化剂物质的量分数为5%的条件下,纳米多孔钯可以高效催化亚胺化合物的加氢还原反应,高选择性、高产率地生成一系列仲胺,仲胺的产率在93%~96%之间.该反应官能团兼容性好,底物范围广,带有甲基、甲氧基、氰基和羟基等基团的亚胺都可以顺利发生还原反应生成相应的仲胺.催化剂重复使用5次后,活性未出现明显降低.     

Transfer hydrogenation of ketones catalyzed by ruthenium complexes

Oxidation of 1,3,5- and 1,2,4-trimethylbenzenes using heteropoly vanadomolybdate as catalyst in the presence of hydrogen peroxide under homogeneous conditions has been investigated. Phenol formation in the case of 1,2,4-trimethylbenzene and only side chain oxidation in the case 1,3,5-trimethylbenzene were observed. This behavior is explained in terms of the charge densities on different centers of both substrate molecules calculated by the MNDO method.     

Allylic alkylation of benzoimidazole catalyzed by palladium complexes

Bis(dibenzylidenacetone)palladium is an efficient and highly selective catalyst for the formation ofN-(2,7-dimethylocta-2,7-dienyl)benzoimidazole in the allylation of benzoimidazole withN-(2,7-dimethylocta-2,7-dienyl)-N-methylpiperidinium iodide in the presence of NaH. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 357–360, February, 1999.     

Selective hydrogenation of chloronitrobenzenes catalyzed by palladium complex of silica-supported chitosan

A palladium complex of silica-supported chitosan has been found to catalyze the hydrogenation of p-, m- and o-chloronitrobenzene, and of 4-chloro-1,3-dinitrobenzene to p-, m- and o-chloroaniline, and 4-chloro-3-aminoaniline in 100% yield, respectively, at room temperature and under atmospheric pressure, and the side reaction, dechlorination, has not been observed. This catalyst was very stable, the turnover numbers (p-chloronitrobenzene to p-chloroaniline cycles / palladium atom) reached 9000 in 17 hours.