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Keggin-type polyoxotungstates as catalysts in the oxidation of cyclohexane by dilute aqueous hydrogen peroxide

1999; Elsevier BV; Volume: 144; Issue: 3 Linguagem: Inglês

10.1016/s1381-1169(99)00025-4

1873-314X

Mário M.Q. Simões, Cassandra Conceição, José A. F. Gamelas, Pedro Domíngues, Ana M. V. Cavaleiro, José A. S. Cavaleiro, A. J. Ferrer‐Correia, R. A. W. Johnstone,

Chemical Synthesis and Reactions

Oxidation of cyclohexane by hydrogen peroxide in the presence of catalytic amounts of the Keggin-type heteropolytungstates [PW11O39]7− and [PW11M(L)O39](7−m)−, Mm+=first row transition metal cation, L=H2O or CH3CN, was found to produce cyclohexanol, cyclohexanone and, in certain cases, cyclohexyl hydroperoxide. The presence of the latter was demonstrated by negative chemical ionization GC-MS. The reactions were carried out in acetonitrile, using tetra n-butylammonium salts of the catalysts and aqueous 30% hydrogen peroxide as oxidant. The polyanions [PW11O39]7− and [PW11Fe(H2O)O39]4− showed higher catalytic activity and different selectivity for the oxidation of cyclohexane than did the corresponding Cu-, Co-, Mn- and Ni-substituted complexes.