Theoretical Study of the Oxidation of Nickel Thiolate Complexes by O2

Qualitative ab initio theory is used to compare the electronic structures of nickel dithiolate complexes and the monosulfinates arising from O2 oxidations. The results are used to examine the electronic factors involved in the reaction mechanism. The frontier molecular orbitals (FMOs) of the dithiolate complexes are dominated by contributions from S p orbitals. Upon oxidation, the FMOs are dominated by sulfinate O atoms. This is consistent with a mechanism involving nucleophilic attack on O2 by the thiolate S-donors and suggests that the reaction stops after the oxidation of a single S atom because of this change in electronic structure.