A pentacoordinated triphosphine benzenedithiolatoiron(II) complex containing a vacant site for binding has been prepared and characterized. The complex is found to be a robust proton reduction catalyst with an overpotential of 0.56 V and a turnover frequency of 2900 s(-1) with respect to 0.28 M acetic acid as the proton source. A mechanism describing the electroproton reduction process has been proposed.