Theoretical study of olefin oxidation process on a dioxo-mu-oxo Mo catalyst

摘要

The dimeric complex dioxo (mu-oxo) thiocyanato of molybdenum(VI) bearing a 4,4'-di-ter-butyl-2,2'-bipyridine ligand in trans conformation (complex 1) has been used in catalytic reactions of olefins (ethylene) oxidation, giving as intermediate a dimeric complex oxo bis (mu-oxo) thiocyanato of molybdenum(V) in cis conformation (complex 2). Binding and electronic properties were calculated using the parametric quantum chemistry method for catalytic reactions, CATIVIC. The interaction of an ethylene molecule with complex 3 (cis version of complex 1) leads to the formation of the intermediate named complex 4. This complex is dissociated to form complex 5 plus ethylene oxide. Changes of electronic and bonding properties are analyzed in terms of atomic charge, orbital population, total binding energies, diatomic bond energies, diatomic energies, and Wiberg indexes, and equilibrium bond distances. The energy balance for the complete catalytic process is presented in a schematic way. Results confirm the extraordinary oxo-transfer abilities of this complex, considering that the whole process is exothermic (-44 kcal/mol). Regeneration of the catalyst is also calculated by the interaction of H2O2 with complex 5. (c) 2008 Wiley Periodicals, Inc.