Organotin-oxomolybdate coordination polymers as catalysts for the epoxidation of cyclooctene

Abstract

The organotin-oxomolybdate coordination polymers [(R 3Sn) 2MoO 4]· nH 2O (R = methyl, n-butyl, cyclohexyl, phenyl, benzyl) were tested as catalysts for the liquid-phase epoxidation of cyclooctene with 30% aqueous hydrogen peroxide at 35 °C and atmospheric pressure. Water, acetonitrile and dichloromethane were examined as additional co-solvents for the reaction. The catalytic results vary considerably with the nature of the tin-bound R group and the co-solvent. For all systems, cyclooctene oxide was the only observed reaction product. Apart from the trimethyltin derivative, the best results were obtained without additional co-solvent or with CH 2Cl 2, while addition of water or CH 3CN had a detrimental effect on catalytic performance. The highest turnover frequency ( 46 mol mo l Mo − 1 h − 1 ) was obtained for the system containing the tri- n-butyltin derivative as catalyst and CH 2Cl 2 as solvent. Complete conversion of the substrate was achieved for this system within 4 h. Using water instead of CH 2Cl 2 with the n-butyl catalyst reduced the catalytic activity considerably at the beginning of the reaction, although 91% conversion was achieved after 24 h. The behavior of the trimethyltin derivative was atypical in that conversion of cyclooctene was only possible when CH 3CN was used as the co-solvent. Experiments were also carried out using a urea/hydrogen peroxide adduct as a water-free source of H 2O 2. However, the catalytic activities observed were significantly lower than those obtained using aqueous H 2O 2.