[3Â +Â 2] Versus [2Â +Â 2] addition of metal oxides across CC bonds: A theoretical study of the mechanisms of oxidation of ethylene by osmium oxide complexes

► In OsO4-ethene reactions [3 + 2] addition is more feasible than [2 + 2] addition. ► OsO2(OH)2-ethene reactions are less feasible than [3 + 2] OsO4-ethene reactions. ► In OsO2Cl2-ethene reactions [2 + 2] addition is more feasible than [3 + 2] addition. ► Epoxide is not a likely product in OsO2Cl2-ethylene reactions.