Vanadium nitrogenase reduction reactions

There is an increasing demand for catalytic reduction reactions involving low-valent transition metals, and this has led to investigations into the redox chemistry of species such as titanium(II or III), vanadium(II) and samarium(II). Low-valent vanadiums and titaniums contribute to reductive transformations as observed in nitrogenase. In addition to the catalytic reduction of organic halides, the construction of efficient catalytic systems for synthetically important catalytic pinacol... 

Thus, a number of systems of the catalytic and noncatalytic reduction of dinitrogen to hydrazin and ammonia and the successful synthesis of model iron- and iron-molibdenum (vanadium) clusters have been reported. These investigations have formed a basis for subsequent progress in mimicking the nitrogenase reaction. 

Acetylene is quantitatively reduced by V catecholate to ethylene with cw-di-deuteroethylene formed selectively from C2D2, also similarly to enzymatic reduction of C2D2 by nitrogenase. Distinct from N2 reduction, the pH range for the reduction of acetylene is much broader than for dinitrogen (from ca pH 5 to concentrated alkali solution). Kinetic studies of the oxidation of vanadium(II) catecholate complex by dinitrogen have led to the reaction equation ... 

Coupling the results from the Mo model complex [57] with the explanation for the presence and possible action of homocitrate, these results provide the best model to date for N2 reduction by conventional molybdenum nitrogenases. Vanadium-dependent nitrogenases probably undergo similar reactions, but iron-only nitrogenases [66] and the unique molybdenum-dependent nitrogenase from Streptomyces thermoautrophicus [67] present further mysteries. 

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