Mechanistic insights into aerobic oxidative cleavage of glycol catalyzed by an Anderson-type polyoxometalate [IMo6O24]5.

Abstract

A computational investigation of the aerobic oxidative C-C bond cleavage reaction of glycol catalyzed by an Anderson-type heteropolyanion HPA [IMo6O24]5- in the presence of acetonitrile as solvent has been performed at the WB97XD/6-31G(d,p)/lanl2dz level. Two reaction pathways have been identified. The catalytic cycle of each pathway consists of three steps: oxidation cleavage of a glycol molecule by the HPA, oxidation of the HPA by one dioxygen molecule, and, finally, oxidation of a second glycol and regeneration of the catalyst. These reaction pathways have been thoroughly investigated in terms of energetic, natural bond orbital (NBO), natural charges, and geometrical parameters. It is found that (i) even though the top oxygen atoms of the Anderson heteropolyanion are not the most negatively charged ones, they are more likely to react with the diol hydroxyl groups, (ii) a direct relationship between the presence of the iodine ion I(VII) and the studied oxidation reaction could not be identified, and (iii) in terms of energy, the transfer of the two hydrogen atoms is the most energetic step.