Density Functional Study on the Mechanism of the Vanadium-Catalyzed Oxidation of Sulfides by Hydrogen Peroxide

Abstract

A computational study with the Becke3LYP method is carried out on the mechanism of the reaction of complexes V(O)(L)(OOH) and V(O)(LH)(OO) (L = O(CH)(3)N(CH(2))(2)O) with CH(3)S-SCH(3), a system that stands as a model for experimental systems where the metal complex contains larger chelating Schiff bases and the substrate is bis(tert-butyl) disulfide. The different possible isomers of both the hydroperoxo V(O)(L)(OOH) and the peroxo V(O)(LH)(OO) forms of the catalyst are explored, and the reactivity of the most stable among them with the dimethyl disulfide substrate is studied through location of the corresponding transition states. A large variety of reactive paths happen to exist, though in all cases the reaction takes place through a direct transfer process, with the simultaneous formation of the S-O bond and breaking of the O-O bond being the rate-limiting step.

Effective oxidation of 1,2-cyclooctene by oxo-vanadium(IV) tetradentate Schiff base complexes under 1 atmosphere of molecular oxygen

“…Similarly, electron-withdrawing substituents on the catalyst are expected to destabilize the metal-oxo intermediate making it a more reactive oxidant. These results of electrochemical studies on catalyst [7][8][9][10]17] provide credence to this supposition. At this stage, we would like to make the following recommendations on the most suitable catalysts for the oxygenation of olefin compounds.…”

“…The oxo-vanadium(IV) complexes of Schiff base take part in a number of interesting oxotransfer reactions [7,8]. Vanadium complexes can also activate molecular oxygen for oxygenation reactions and they have been reported [9,10]. One of the attractive features of salen-based ligand is that the ligands may be tuned both sterically and electronically by the variation of corresponding diamines and salicylaldehyde ligand precursors.…”

Mechanistic Analysis of Nucleophilic Substrates Oxidation by Functional Models of Vanadium‐Dependent Haloperoxidases: A Density Functional Theory Study

“…Density functional theory has been used to address questions regarding reactivity and spectroscopic properties of transition-metal systems related to biology [28] and catalysis. [29] Balcells et al reported computational studies of a truncated QC models for vanadium(V)-containing Schiff base complexes [30] and its ability to oxidize organic disulfides in the presence of hydrogen peroxide. This study was later expanded to determine the factors controlling the stereoselectivity of disulfide oxidation using QM/MM methods [31] on sterically hindered Schiff bases often employed in vanadium catalysis literature.…”

The trigonal-bipyramidal NO4 ligand set in biologically relevant vanadium compounds and their inorganic models

“…The reaction mechanism for the sulfoxygenation is analogous to that for the halide oxygenation, i.e., the active catalyst is the hydroperxo intermediate. DFT calculations suggest that, as in the case of bromide as substrate, sulfides and disulfides are not activated by direct coordination to vanadium (which thus remains in its penta-coordinate array), but rather by direct interaction with the peroxo/hydroperoxo group [18]. In contrast to the halide oxygenation, protons are not consumed; they are, however, necessary as cocatalyst.…”