6533b7d5fe1ef96bd1264568

RESEARCH PRODUCT

Modeling for the active site nitrate reductase. Oxidation of the complex [MovO(O2CC(S) CH3Ph)2]− by nitrate and nitrite in methanol

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Abstract Under acid conditions the [MoVIO2(O2CC(S)CH1Ph)2]2 reacts with thiols to yield the monomeric [MoVO(O2CC(S)CH3Ph)2] and disulfide. The reduced complex [MoVO(O2CC(S)CH3Ph)2]− can react with NO3− and NO2− in a one-electron step yeilding respectively NO2 and NO and the original molybdenum (VI)-dioxo complex. The experimental pseudo-first-order rate constant with respect to the Mo(V) complex at 25°C was found to be kobs=2.3×10−4s−1 for NO3− and kobs=1.0×10−2 for NO2−. Oxo transfers to and from the substrate have been coupled to produce a catalytic system which turns over the reaction RSH+(No3− or NO2−)+H+a 1 2 [ RS ] 2 +( NO ] 2 or NO )+ H 2 O , in which thiols, NO1− and NO2− serve as a model substrates and molybdenum complex as a catalyst. This result has permitted us to consider the system as a possible model for the nitrate reductase ‘Chlorella’ (S.P. Cramer et al., J. Am. Chem. Soc., 106 (1984) 1467; G.N. Geoige et al., Biochem. J., 259 (1989) 693).