Polymer supported vanadium and molybdenum complexes as potential catalysts for the oxidation and oxidative bromination of organic substrates.
The Schiff base (H2fsal-ohyba) derived from 3-formylsalicylic acid and o-hydroxybenzylamine has been covalently bonded to chloromethylated polystyrene cross-linked with 5% divinylbenzene (abbreviated as PS-H(2)fsal-ohyba, I). Treatment of [VO(acac)2] with PS-H2fsal-ohyba in dimethylformamide (DMF) gave the oxovanadium(iv) complex PS-[VO(fsal-ohyba).DMF] (1). Complex 1 can be oxidized into the dioxovanadium(v) species, PS-K[VO2(fsal-ohyba)] (2) on aerial oxidation in the presence of KOH or into the oxoperoxo species, PS-K[VO(O2)(fsal-ohyba)] (3) in the presence of H2O2 and KOH in DMF suspension. Similarly, PS-[MoO(2)(fsal-ohyba).DMF] (4) has been isolated by the reaction of [MoO2(acac)2] with PS-H2fsal-ohyba. All these complexes have been characterised by various techniques. These complexes catalyse the oxidation of styrene, ethylbenzene and phenol efficiently. Styrene gives five reaction products namely styrene oxide, benzaldehyde, 1-phenylethane-1,2-diol, benzoic acid and phenylacetaldehyde, while ethylbenzene gives benzaldehyde, phenyl acetic acid, styrene and 1-phenylethane-1,2-diol. The oxidation products of phenol are catechol and p-hydroquinone. These catalysts are also able to catalyse the oxidative bromination of salicylaldehyde to 5-bromosalicylaldehyde with ca. 80% selectively in the presence of aqueous 30% H2O2/KBr, a reaction similar to that exhibited by vanadate-dependent haloperoxidases. Their corresponding neat complexes have also been prepared and their catalytic activities have been compared.
Maurya
Mannar R
MR
Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667, India. rkmanfcy@iitr.ernet.in
Kumar
Umesh
U
Manikandan
P
P
D000447:Aldehydes / Q000737:chemistry; D001555:Benzene Derivatives / Q000737:chemistry; D001965:Bromides / Q000737:chemistry*; D002384:Catalysis; D006861:Hydrogen Peroxide / Q000737:chemistry; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008855:Microscopy, Electron, Scanning; D008982:Molybdenum / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D020058:Styrene / Q000737:chemistry; D013818:Thermogravimetry; D014639:Vanadium / Q000737:chemistry*
D000447:Aldehydes; D001555:Benzene Derivatives; D001965:Bromides; D008024:Ligands; D009930:Organic Chemicals; D010636:Phenols; D011108:Polymers; D014639:Vanadium; C013243:salicylaldehyde; D020058:Styrene; D008982:Molybdenum; D006861:Hydrogen Peroxide; C004912:ethylbenzene