Catalytic Reduction of cis-Dimethyldiazene by the [MoFe3S4]3+ Clusters. The Four-Electron Reduction of a NN Bond by a Nitrogenase-Relevant Cluster and Implications for the Function of Nitrogenase

• Published in: Journal of the American Chemical Society Vol. 119; no. 7; pp. 1662 - 1667
• Main Authors: Malinak, Steven M, Simeonov, Anton M, Mosier, Patrick E, McKenna, Charles E, Coucouvanis, Dimitri
• Format: Journal Article
• Language: English
• Published: American Chemical Society 19.02.1997
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja963475s

The catalytic reduction of cis-dimethyldiazene by the (Et4N)2[(Cl4-cat)(CH3CN)MoFe3S4Cl3] cluster (Cl4-cat = tetrachlorocatecholate) is reported. Unlike the reduction of cis-dimethyldiazene by the Fe/Mo/S center of nitrogenase, which yields methylamine, ammonia, and methane (the latter from the reduction of the C−N bond), the reduction of cis-dimethyldiazene by the synthetic cluster yields exclusively methylamine. In separate experiments, it was shown that the C−N bond of methylamine is not reduced by the [MoFe3S4]3+ core, perhaps accounting for the differences observed between the biological and abiological systems. 1,2-Dimethylhydrazine, a possible partially reduced intermediate in the reduction of cis-dimethyldiazene, was also shown to be reduced to methylamine. Interaction of methylamine with the Mo atom of the cubane was confirmed through the synthesis and structural characterization of (Et4N)2[(Cl4-cat)(CH3NH2)MoFe3S4Cl3]. Phosphine inhibition studies strongly suggest that the Mo atom of the [MoFe3S4]3+ core, which has a Mo coordination environment very similar to that in nitrogenase, is responsible for the binding and activation of cis-dimethyldiazene. The reduction of a NN bond exclusively at the heterometal site of a nitrogenase-relevant synthetic compound may have implications regarding the function of the nitrogenase Fe/Mo/S center, particularly in the latter stages of dinitrogen reduction.