Tungsten complexes catalyzed methyl formate formation

The monoanionic tungsten complex W[S2C2Ph(p-MeOPh)]3 has been reported to catalyze formation of hydrogen from water, using free radicals derived from methyl viologen as the source of electrons (112). The catalytic cycle has been proposed to involve sequential electron and proton transfer. 

Acetogenic bacteria such as Clostridium (Cl.) ther-moaceticum or Cl. formicoaceticum catalyze an NADPH2-driven CO2 reduction to formate, which is further reduced via the tetrahydrofolate pathway to the -CH3 oxidation state, as the methyl is finally incorporated into acetic acid. This anabolic formate dehydrogenase has long been known to depend on the presence of Se in the medium for its formation. The enzyme is an ai 2 heterooligomer of 340 kDa the complex contains two selenocysteine residues, two moles of a tungsten cofactor, and Fe/S centers. 

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