Selective oxidation of alkenes catalysed by ruthenium(II) complexes containing coordinated perchlorate
TL;DR: In this paper, the selective homogeneous oxidation of cyclohexene with TBHP and H2O2 as oxidizing agents was investigated. And the results showed that TBHP was more effective than H 2 O 2 as an oxidizing agent.
Abstract: Ruthenium(II) perchlorate complexes, [Ru(dppm)3(ClO4)]ClO4 1, [Ru(dppe)3(ClO4)]ClO4 2, and [Ru(dpae)3(ClO4)]ClO4 3, catalyse the selective homogeneous oxidation of alkenes with TBHP and H2O2 as oxidizing agents. Oxidation of cyclohexene with TBHP gave 2-cyclohexene-1-ol, 2-cyclohexenone and 1-(tert-butylperoxy)-2-cyclohexene. The homogeneous liquid phase oxidation of cyclohexene with TBHP shows appreciable solvent effect. Styrene on oxidation with TBHP gave benzaldehyde as the major product and styrene oxide as the minor product. Oxidation with H2O2 is radical-initiated and gives low conversion to products. TBHP and H2O2 are compared for their oxidizing ability and TBHP is more effective than H2O2 as an oxidizing agent. Linear and long chain alkenes are not efficiently oxidized. Cyclooctene and trans-stilbene are oxidized to the corresponding epoxides.
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TL;DR: In this article, a simple physical-vapor-infiltration (PVI) method was applied to prepare highly ordered Fe-containing mesoporous silica SBA-15.
Abstract: A simple physical-vapor-infiltration (PVI) method was applied to prepare highly ordered Fe-containing mesoporous silica SBA-15. The loading amount of Fe in SBA-15 was very high (up to 24 mol%) and can be tuned by using different PVI time. The liquid phase selective oxidation of styrene with H 2 O 2 has been used to characterize their catalytic properties, the major product is benzaldehyde and the minor is styrene oxide. Independent of the Fe contents and the heat treatment temperature, the selectivity for benzaldehyde in the reaction at a mild temperature of 50 °C are all above 91%. At elevated temperature of 70 °C, the conversion rate of styrene increases beyond 36% and more significantly the selectivity for benzaldehyde can reach as high as 99%. Comparatively, another two different schemes (simple wet impregnation and incorporation using silane coupling agent) have been also applied to synthesize Fe-containing SBA-15 samples. Under the same condition, the styrene conversion on these two samples are both very low with minor product of phenylacetaldehyde and other styrene oxides.
41 citations
TL;DR: In this paper, the coupling of microwave energy with solvent-free phase-transfer catalysis was studied for the oxidation of cyclohexene and styrene, and parallel oxidations were successfully employed by using a special microwave set-up.
35 citations
TL;DR: In this paper, an environmentally benign oxidation of alcohols and alkenes over transition metal substituted phosphomolybdates with molecular oxygen as an oxidant and TBHP as an initiator was carried out.
32 citations
TL;DR: In this paper, the authors used a robust biosorption system consisting of a bacterial biofilm, Arthrobacter viscosus, supported on zeolite NaY.
Abstract: The goal of this study is the preparation of new heterogeneous catalytic materials to be used in oxidation reactions under mild conditions through the valuation of heavy metals in wastewater. The samples used in the immobilization of chromium complexes were prepared from a dichromate solution of 100 mgCr L � 1 . The zeolite CrNaY was prepared from a robust biosorption system consisting of a bacterial biofilm, Arthrobacter viscosus, supported on zeolite NaY. The biofilm performs the reduction of Cr(VI) to Cr(III) and this cation is retained in the zeolite by ion exchange. The immobilization of chromium complexes with heterocyclic ligands in the supercages of Y zeolite was performed by the in situ synthesis with three different ligands, 3-methoxy-6-chloropyridazine (A), 3-piperidino-6-chloropyridazine (B) and 1-(2pyridylazo)-2-naphthol (C). A sample loaded with Cr from a liquid solution with the same initial concentration was prepared as a reference through the traditional direct ion-exchange method and coordinated with ligand (A). The resulting catalysts were fully characterized by different techniques (FTIR, XRD, TGA, SEM, Raman, cyclic voltammetric studies and chemical analysis) and the results confirmed that the Cr complexes were immobilized in supercages of NaY. Catalytic studies were performed in liquid phase for the cyclohexene oxidation, at 40 8C, using tert-butyl hydroperoxide (TBHP) as the oxidizing agent. All the prepared catalysts exhibited catalytic activity for the oxidation reaction.
29 citations
TL;DR: In this article, Co2+ exchanged supported 12-tungstophosphoric acid was synthesized and characterized for the oxidation of alkenes such as styrene, cyclohexene, and cis-cyclooctene under mild conditions.
Abstract: Co2+ exchanged supported 12-tungstophosphoric acid was synthesized and characterized. Its catalytic activity was evaluated for the oxidation of alkenes such as styrene, cyclohexene and cis-cyclooctene under mild conditions. The superiority of the catalyst lies efficiently in catalyzing the non-solvent liquid phase oxidation of alkenes, especially oxidation of cyclohexene with 98% conversion and 57% selectivity for cyclohexene oxide, with molecular oxygen at 1 atm pressure. The active intermediate, responsible for the oxidation of alkenes, was also isolated and characterized by ESR. Its catalytic activity was evaluated for the oxidation of styrene under optimized conditions. Based on the above study a probable reaction mechanism was also proposed.
28 citations
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TL;DR: In this article, the pH dependence of the redox chemistry of [Ru(dmphen)2(H2O)]2+ has been measured and the results were used to provide a mechanism for the catalysis of alkane oxidation by this complex.
Abstract: The pH dependence of the redox chemistry of [Ru(dmphen)2(H2O)]2+ has been measured (dmphen = 2,9-dimethyl-1, 10-phenanthroline). Comparison of the results with those for similar complexes illustrates the unique acidity of the co-ordinated waters and the large oxidizing strength of the ruthenium. The reaction of [Ru(dmphen)2(H2O)2]2+ with H2O2 has been studied as a function of pH and the results are used to provide a mechanism for the catalysis of alkane oxidation by this complex.
19 citations
TL;DR: Cations formed on O-coordination of N-nitrosodimethylamine with different electrophiles decomposed by different routes: dissociation of Me 2 N = NOCMe 3 + ClO 4 − to Me 2 n = NOH + Cl O 4 − ; regeneration of free nitrosamine by nucleophilic cleavage of the O-Si bond in Me 2N = NOSiMe 3+CF 3 + CF 3 SO 3 − ; and nucleophilicity displacement of the N-methyl groups from Me 2n 2 N 2
18 citations
TL;DR: In this article, the FeII complex with macrocycle cyclam (1,4,8,11-tetraazacyclotetradecane) reacts with H2O2 in acetonitrile to give a mixture of products which results from oxidation both at the metal center and the ligand.
17 citations
TL;DR: In this paper, the Ru and Rh complexes have been used in non-radical, coordination catalysis for catalyzed O 2 -or air-oxidations because of the cheapness and environmental compatibility of the oxidant and its reduction product, water.
Abstract: Studies continue to intensify on catalyzed O 2 - or air-oxidations because of the cheapness and environmental compatibility of the oxidant and its reduction product, water. Complexes of Ru and Rh have figured prominently in such studies, and this paper emphasizes developments using Ru and Rh complexes in nonradical, coordination catalysis. Both dioxygenase- and monooxygenase-type activity have been realized, in which both O-atoms, or one O-atom of O 2 , respectively, are incorporated in the oxidizable substrate. Oxidations effected include: CO to CO 2 , H 2 to H 2 O 2 , phosphines and sulfides to their oxides, olefins to epoxides and/or ketones, alcohols to ketones or aldehydes, aldehydes and ketones to (per)acids, saturated hydrocarbons to alcohols, and phenol to p -hydroquinone. Oxidative dehydrogenations of alcohols and amines (oxidase-type activity) have also been effected.
15 citations