Vanadium complexes sulfur ligands

Dithiothreitol is a more complex ligand than p-mercaptoethanol, and there is a corresponding increase in complexity of the solution chemistry. Two binuclear products (-352, -362 ppm -399, -526 ppm), both of V2L stoichiometry, have been identified. The individual vanadiums of each product are chemically distinct. The NMR studies [37] show that in one of the complexes, both vanadiums have a single coordinated sulfur. In the second complex, one of the two vanadiums has sulfur coordinated, whereas the second of the two has only oxygen in the coordination sphere. Neither of these compounds have been characterized by x-ray diffraction... 

The Vra complex with L-cysteine was prepared and characterized the crystal structure shows a 1 2 stoichiometry and that the two S-donors are trans to one another while the O- and N-donors are cis to one another (194).810 With three different donor functionalities, this 1 2 complex illustrates key aspects of Vm coordination chemistry. To identify the mode of action of cellular vanadium species and the roles of cysteine and glutathione in cellular redox chemistry, the redox and complexation chemistry of vanadium with sulfur-containing ligands must be better... 

Selection of vanadium complexes with multifunctional ligands including sulfur. See refs 57b-61. 

Nxumalo, F. and A.S. Tracey. 1998. Reactions of vanadium(V) complexes of N,N-dimethylhydroxylamine with sulfur-containing ligands Implications for protein tyrosine phosphatase inhibition. J. Biol. Inorg. Chem. 3 527-533. 

The most direct way to prepare VO(acac)2 is by the reaction of vanadyl sulfate with a source of the ligand. Vanadium(V), such as V205, can be reduced to vanadium(IV) by ethanol solvent in the presence of sulfuric acid. Reaction with acetylacetone in sodium carbonate yields the desired product. The synthesis we will use produces the complex in high yield directly in a system that can visually shed light on the active catalyst species in the epoxidation of olefins, Figure 9.4. 

Vanadium (II) complexes with sulfur-donor ligands are relatively rare. Those reported are prepared from the usual precursors noted above. Thus... 

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