Synthesis, redox chemistry, and X-ray structure of the mixed-metal clusterFe-2(CO)(6)(mu(3)-S)(2)Ni (dppf)

The reaction between the dianion [Fe-2(CO)(6)(mu(2)-S)(2)](2-) and NiCl2(dp pf) occurs readily at room temperature to give the mixed-metal cluster Fe-2 (CO)(6)(mu(3)-S)(2)Ni(dppf) in moderate yield. Fe-2(CO)(6)(mu(3)-S)(2)Ni(dp pf) was isolated by preparative chromatography and its solid-state structur e established by X-ray diffraction analysis. Fe-2(CO)(6)(mu(3)-S)(2)Ni(dppf ) crystallizes in the monoclinic space group C2/c, a = 20.320(6), b = 13.11 4(2), c = 15.622(2) Angstrom, beta = 110.25(2)degrees V = 3905.4(11) Angstr om(3), Z = 4, and d(calc) = 1.630 g/cm.(3) The X-ray structure of Fe-2(CO)( 6)(mu(3)-S)(2)Ni(dppf) exhibits an Fe2S2Ni arachno polyhedral core, with th e pendant dppf ligand attached to an essentially square planar Ni center. T he redox chemistry of Fe-2(CO)(6)(mu(3)-S)(2)Ni(dppf) was investigated by c yclic voltammetry which showed a reversible, one-electron oxidation localiz ed on the Fe2S2 core along with an irreversible, one-electron reduction tha t is antibonding with respect to the Fe-Fe and Fe-S bonds. The electrochemi cal assignments were confirmed by carrying out extended Huckel MO calculati ons on the model cluster Fe-2(CO)(6)(mu(3)-S)(2)Ni(H-4-dppf).