Issue 33, 2013

A new binuclear oxovanadium(v) complex as a catalyst in combination with pyrazinecarboxylic acid (PCA) for efficient alkane oxygenation by H2O2

Abstract

A new binuclear oxovanadium(V) complex [{VO(OEt)(EtOH)}2L] (1) where H4L is bis(2-hydroxybenzylidene)terephthalohydrazide has been synthesized and fully characterized. The combination of 1 with pyrazine-2-carboxylic acid (PCA; a cocatalyst) affords a catalytic system for the efficient oxidation of saturated hydrocarbons, RH, with hydrogen peroxide and air in acetonitrile solution at 50 °C to produce alkyl hydroperoxides, ROOH, as the main primary products. Very high turnover numbers (TONs) have been attained in this reaction: for example, after 2220 min, TON = 44 000 and initial TOF (turnover frequency) = 3300 h−1 per molecule of complex 1. The estimated activation energy of the cyclohexane oxygenation in the presence of 1/PCA is Ea = 16 ± 2 kcal mol−1. This value is identical to that obtained for the cyclohexane oxidation with H2O2 catalyzed by the (n-Bu4N)[VO3]/PCA combination (17 ± 2 kcal mol−1). The dependences of initial oxidation rates W0 on the initial concentrations of all components of the reaction mixture have been determined. Based on these kinetic data and on the regio- and bond-selectivity parameters measured in the oxidation of linear and branched alkanes a mechanism of the oxidation has been proposed which includes the generation of hydroxyl radicals in the crucial stage.

Graphical abstract: A new binuclear oxovanadium(v) complex as a catalyst in combination with pyrazinecarboxylic acid (PCA) for efficient alkane oxygenation by H2O2

Supplementary files

Article information

Article type
Paper
Submitted
03 Mar 2013
Accepted
04 Apr 2013
First published
04 Apr 2013

Dalton Trans., 2013,42, 11791-11803

A new binuclear oxovanadium(V) complex as a catalyst in combination with pyrazinecarboxylic acid (PCA) for efficient alkane oxygenation by H2O2

M. Sutradhar, N. V. Shvydkiy, M. F. C. Guedes da Silva, M. V. Kirillova, Y. N. Kozlov, A. J. L. Pombeiro and G. B. Shul'pin, Dalton Trans., 2013, 42, 11791 DOI: 10.1039/C3DT50584G

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