METALLAOXETANES AS POSSIBLE INTERMEDIATES IN METAL-PROMOTED DEOXYGENATION OF EPOXIDES AND EPOXIDATION OF OLEFINS

Calculations including electron correlation have been performed for the insertion of a number of first and second row transition metal atoms (Cr, Co, Fe, Ni, Cu, Mo, Ag) into the C-O bond of ethene oxide. It is found that for all these metals, except silver, a metallacycle is more stable than the [metal + epoxide]. The energy of [metal + epoxide] is also compared to [metal oxide + ethene] and it is found that only for copper and silver is [metal + epoxide] lower in energy than [metal oxide + ethene]. The difference between the metals in this respect is explained by the difference in binding energy of the diatomic metal oxides. Silver and copper have much weaker M = O bonds than the rest of the metals studied, and this favors an epoxidation reaction.