Polystyrene bound oxidovanadium(IV) and dioxidovanadium(V) complexes of histamine derived ligand for the oxidation of methyl phenyl sulfide, diphenyl sulfide and benzoin

Abstract

Ligand Hsal-his (I) derived from salicylaldehyde and histamine has been covalently bound to chloromethylated polystyrene cross-linked with 5% divinylbenzene. Upon treatment with [VO(acac)(2)] in DMF, the polystyrene-bound ligand (abbreviated as PS-Hsal-his, II) gave the stable polystyrene-bound oxidovanadium(iv) complex PS-[V(IV)O(sal-his)(acac)] , which upon oxidation yielded the dioxidovanadium(v) PS-[V(V)O(2)(sal-his)] complex. The corresponding non polymer-bound complexes [V(IV)O(sal-his)(acac)] and [V(V)O(2)(sal-his)] have also been obtained. These complexes have been characterised by IR, electronic, (51)V NMR and EPR spectral studies, and thermal as well as scanning electron micrograph studies. Complexes and have been used as a catalyst for the oxidation of methyl phenyl sulfide, diphenyl sulfide and benzoin with 30% H(2)O(2) as oxidant. Under the optimised reaction conditions, a maximum of 93.8% conversion of methyl phenyl sulfide with 63.7% selectivity towards methyl phenyl sulfoxide and 36.3% towards methyl phenyl sulfone has been achieved in 2 h with 2 . Under similar conditions, diphenyl sulfide gave 83.4% conversion where selectivity of reaction products varied in the order: diphenyl sulfoxide (71.8%) > diphenyl sulfone (28.2%). A maximum of 91.2% conversion of benzoin has been achieved within 6 h, and the selectivities of reaction products are: methylbenzoate (37.0%) > benzil (30.5%) > benzaldehyde-dimethylacetal (22.5%) > benzoic acid (8.1%). The PS-bound complex, 1 exhibits very comparable catalytic potential. These polymer-anchored heterogeneous catalysts do not leach during catalytic action, are recyclable and show higher catalytic activity and turnover frequency than the corresponding non polymer-bound complexes. EPR and (51)V NMR spectroscopy was used to characterise methanolic solutions of 3 and 4 and to identify species formed upon addition of H(2)O(2) and/or acid and/or methyl phenyl sulfide.

Structural models of vanadate-dependent haloperoxidases, their reactivity, immobilization on polymer support and catalytic activities

“…22 Conversion of 4 into the peroxido complex 7 by the treatment with H 2 O 2 represents the formation of an intermediate similar to that found in the catalytic cycle 28 of VHPO. 23 The stability of 7 is poor and decomposes slowly at room temperature.…”

“…Original spectrum can also be obtained The removal of sulfur compounds from petroleum products has attracted attention of researchers to fulfill the demand of environment friendly fuels. The oxidation of model organosulfur compounds with sulfur concentrations of 500 ppm was tested in heptane using catalysts PS-[V IV O(OMe)(fsal-dmen)] (27) and PS-[V V O 2 (fsal-dmen)] (28) in the presence of 30% H 2 O 2 . The results are summarized in table 5.…”

“…Immobilization of [V IV O(acac)(sal-his)] (15) to give PS-[V IV O(acac)(sal-his)](23) involved the reaction of Hsal-his (VI) with chloromethylated polystyrene, cross-linked with 5% divinylbenzene in DMF in the presence of triethylamine followed by reaction of Scheme for the synthesis of oxidovanadium(IV) and dioxidovanadium(V) complexes. Scheme for the synthesis of polymer-supported complexes 28. 1 st derivative EPR spectra of PS-[V IV O(acac)(sal-his)] (23): (a) solid at room Temperature, (b) in contact with DMF at 77 K; and [VO IV (acac)(sal-his)] (15): (c) in MeOH at 77 K, (d) in DMF at 77 K. 28…”

Chemistry of molecular and supramolecular structures of vanadium(IV) and dioxygen-bridged V(V) complexes incorporating tridentate hydrazone ligands

“…However, at pharmacological concentrations, some species are potential therapeutic agents [3,4]. Thus, the insulin-enhancing, insulin mimetic properties of oxovanadium(V) complexes, their use as model complexes for the active site of vanadoenzymes, and their use as catalysts in biological and industrial processes have been reported [5][6][7][8][9]. Furthermore, these compounds exhibit potential as anti-tumour agents by inhibiting growth of malignant cell lines by induction of cell-cycle arrest and/or cytotoxic effects [10].…”

Towards the Development of Fiber-Based Oxidovanadium(IV) Catalysts for the Oxidation of Thioanisole

“…A great deal of research at the moment is focussed around immobilizing these homogeneous catalysts onto solid supports [15,16]. Although homogeneous catalysts often exhibit improved activity over their heterogeneous counterparts, they are rarely applied to the chemical and petrochemical industries [6].…”