Investigation of the catalytic activity of metal complexes fixed on a solid support. 10. Selective hydrogenation of allylbenzene in the presence of heterogeneous Pt-Sn-citrate complexes

New heterogeneous catalysts based on the complexes of platinum with tin(II) citrate were prepared. The catalysts exhibit high selectivity in the hydrogenation of allylbenzene to propylbenzene without increasing the rate of isomerization of the C=C bond. The activity of the complexes depends on the conditions and decreases with increase in the Sn:Pt ratio.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. St. Petersburg Technological Institute. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1287–1290, June, 1992.     

Tuning catalytic activity of dimolybdenum paddlewheel complexes by ligands: mechanism study on the radical addition reaction of CCl4 to 1-hexene

Structural Chemistry - The detailed catalytic mechanism of a series of paddlewheel complexes [Mo2L4] featuring Mo-Mo quadruply-bond on radical addition of CCl4 to 1-hexene was studied using density...     

Pd nanoparticles dispersed on solid supports: synthesis,characterization and catalytic activity on selective hydrogenation of olefins in aqueous media

Two types of Pd nanoparticle catalysts were prepared having 2–4 nm particle size using silica gel and porous polymer beads as solid supports. 2‐Pyridinecarboxaldehyde ligand was anchored on commercially available 3‐aminopropyl‐functionalized silica gel followed by Pd metal dispersion. Bead‐shaped cross‐linked poly(4‐vinylpyridine‐co‐styrene) gel was prepared by an emulsifier‐free emulsion polymerization of 4‐vinylpyridine, styrene and divinylbenzene in the presence of ammonium persulfate and subsequently dispersing the Pd metal on the synthesized polymer. These catalysts were characterized by SEM, TEM and ICP techiniques with respect to appearance, size and possible leaching out, respectively. Furthermore, the reactivity of these catalysts was tested on hydrogenation of various α,β‐unsaturated carbonyl compounds using aqueous solvent under a hydrogen balloon (1 atm). The results showed that the Pd dispersed on silica was a more efficient catalyst than Pd dispersed on polymer and the former could be recycled more than 10 times without considerable loss in activity. Copyright © 2010 John Wiley & Sons, Ltd.     

Study of amino ligands fixation to macroporous supports and their influence on albumin adsorption

Heterogeneous networks of ethylene glycol dimethacrylate and 2‐hydroxyethyl methacrylate [poly(EGDMA‐co‐HEMA)] were synthesized by suspension polymerization using different EGDMA contents and agitation speeds. The networks were actived with epichlorhydrine (Ech) or 1,4‐butanediol diglycidyl ether (BDGE), and then hexamethylenediamine (HMDA) or ethylenediamine (EDA) were conjugated to the support by coupling reaction. Here, a higher alkyldiamine concentration and temperature, and a longer reaction time led to higher yields. Amino ligands of the support III were used to analyze their adsorption performance of bovine serum albumin (BSA) from the adsorption kinetic. A more external location of HMDA amino ligands into network led to get the maximum adsorption in a time shorter than that with EDA. Due to its bigger size, the HMDA molecule was attached mostly to the network surface between larger pores, which favored a faster protein adsorption. When derivatives containing BDGE were compared, the EDA ligand displayed a BSA retention higher than that with HMDA, because a shorter separation between the ammonium groups along the spacer arm yielded a stronger electrostatic attraction on the protein. Clearly, the balance obtained between the pores system and the reagents molecular structure used in the formation of Ech‐HMDA generated the most efficient BSA adsorption. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Preparation of silica-supported polysulfoalumoxane–platinum complexes and their catalytic activity in the hydrogenation of aromatics

A novel inorganic polymer, silica-supported polysulfoalumoxane, has been prepared and used as a support for preparing a silica-supported polysulfoalumoxane–platinum complex. It has been used as a catalyst for the hydrogenation of aromatics under mild conditions. The effects of several reaction parameters such as metal loading, temperature and solvents on the hydrogenation of methyl benzoate have been studied. The catalyst showed high activity and selectivity.     

Structure and catalytic activity of metallocomplexes immobilized on supports 4. Heterogenized complexes of Rh(II) in reactions of hydrogenation and hydrogen transfer

Acetate, acetonitrile, sulfate, and hexafluoroacetylacetonate binuclear complexes of Rh(II) have been heterogenized on -aminopropyl-containing silica gel and on polymers containing 3(5)-methylpyrazole and imidazole groups. Possible paths of surface structure formation have been examined. It has been shown by means of EPR spectrometry, x-ray photoelectron spectroscopy, and electronic spectroscopy that when [Rh₂(CO₂CCH₃)₄] is deposited on -aminopropylcontaining silica gel and on polymers, the binuclear structure and the degree of oxidation of the metal remain unchanged. Heterogenization of the sulfate, acetonitrile, or hexafluoroacetylacetonate binuclear complexes of Rh(II) takes place with rupture of the Rh-Rh bond and an increase in the degree of oxidation of the central atom. The immobilized complexes manifest activity in allylbenzene hydrogenation and isomerization and also in the reaction of hydrogen transfer from 2-propanol to cyclohexanone. It has been shown that the complexes containing Rh(II) manifest higher activities in these reactions in comparison with the Rh(III) complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 311–317, February, 1991.     

Structure and catalytic activity of metal complexes on carriers 3. Rhodium complexes on modified polymers and their catalytic properties in the reduction of nitrobenzene by chemically bound hydrogen

Heterogenized catalysts based on rhodium complexes attached to polymers modified by the groups 3(5)-methylpyrazole, imidazole and benzimidazole have been synthesized. The process of their formation has been investigated by IR, UV, and EPR spectroscopy. Results have been obtained for the catalytic activity of the complexes in the hydrogenation of nitrobenzene by hydrogen transfer from propan-2-ol and NaBH₄.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, pp. 268–273, February, 1990.     

Immobilization of transition metal ion complexes and their catalytic activity towards the activation of hydrogen peroxide

Transition metal ion-imidazole complexes have been immobilized on silica, silica–alumina (25%Al₂O₃), and alumina supports by adsorption and functionalization methods. The catalytic activity of these supported complexes in the decomposition of H₂O₂ has been studied. The reaction exhibits first-order kinetics with respect to [H₂O₂] and the quantity of catalyst. The rate of reaction decreases as [H₂O₂]₀ increases. The order of catalytic reactivity is strongly dependent on the type of metal ion, support, and the immobilization method. The complex anchored via adsorption exhibited a higher activity compared to the corresponding complex anchored via functionalization of the surface. The reaction proceed via formation of the peroxo-intermediate, which has an inhibiting effect on the reaction rate. The reaction is enthalpy-controlled as is concluded from the isokinetic relationship. A mechanism is proposed involving the generation of HO₂ radicals from the peroxo-intermediate in the rate-determining step.