Sulfur K-Edge X-ray Absorption Spectroscopy and Density Functional Calculations on Mo(IV) and Mo(VI)═O Bis-dithiolenes: Insights into the Mechanism of Oxo Transfer in DMSO Reductase and Related Functional Analogues

摘要

Abstract: Sulfur K-edge X-ray absorption spectroscopy (XAS) and density functional theory (DFT)ncalculations have been used to determine the electronic structures of two Mo bis-dithiolene complexes,n[Mo(OSi)(bdt)2]n1 and [MoO(OSi)(bdt)2]n1 , where OSi [OSiPh2ntnBu]n1 and bdt benzene-1,2-dithiolate(2 ),nthat model the Mo(IV) and Mo(VI)dO states of the DMSO reductase family of molybdenum enzymes. Thesenresults show that the Mo(IV) complex undergoes metal-based oxidation unlike Mo tris-dithiolene complexes,nindicating that the dithiolene ligands are behaving innocently. Experimentally validated calculations havenbeen extended to model the oxo transfer reaction coordinate using dimethylsulfoxide (DMSO) as a substrate.nThe reaction proceeds through a transition state (TS1) to an intermediate with DMSO weakly bound, followednby a subsequent transition state (TS2) which is the largest barrier of the reaction. The factors that controlnthe energies of these transition states, the nature of the oxo transfer process, and the role of the dithiolenenligand are discussed.