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

Oxidation of cyclohexane by hydrogen peroxide in the presence of catalytic amounts of the Keggin-type heteropolytungstates [PW11O39](7-) and [PW11M(L) O-39]((7 - m)-), Mm+ = first row transition metal cation, L = H2O or CH3CN, was found to produce cyclohexanol, cyclohexanone and, in certain cases, cy clohexyl hydroperoxide. The presence of the latter was demonstrated by nega tive chemical ionization GC-MS. The reactions were carried out in acetonitr ile, using tetra n-butylammunium salts of the catalysts and aqueous 30% hyd rogen peroxide as oxidant. The polyanions [PW11O39](7-) and [PW11Fe(H2O)O-3 9](4-) showed higher catalytic activity and different selectivity for the o xidation of cyclohexane than did the corresponding Cu-, Co-, Mn- and Ni sub stituted complexes. (C) 1999 Elsevier Science B.V. All rights reserved.