Biomimetic [MFe₃S₄]³⁺ cubanes (M = V/Mo) as catalysts for a Fischer-Tropsch-like hydrocarbon synthesis - a computational study.

Nitrogenase is the enzyme primarily responsible for reducing atmospheric nitrogen to ammonia. There are three general forms of nitrogenase based on the metal ion present in the cofactor binding site, namely molybdenum-dependent nitrogenases with the iron-molybdenum cofactor (FeMoco), the vanadium-dependent nitrogenases with FeVco, and the iron-only nitrogenases. It has been shown that the vanadium-dependent nitroge-nases tend to have a lesser efficacy in reducing dinitrogen but a higher efficacy in binding and reducing carbon monoxide. In biomimetic chemistry [MFe₃S₄] (M=Mo/V) cubanes have been synthesized, studied and shown to be promising mimics of some of the geometric and electronic properties of the nitrogenase cofactors. In this work, a DFT study is presented on Fischer-Tropsch catalysis by these cubane complexes, by studying CO binding and reduction to hydrocarbons.   Our work implies that molybdenum has stronger binding interactions with the iron-sulfur framework of the cubane, which results in easier reduction of substrates like N₂H₄. However, this inhibits the binding and activation of CO, and hence the molybdenum-containing complexes are less suitable for Fischer-Tropsch catalysis than vanadium-containing complexes.