A new cumulene diiron complex related to the active site of Fe-only hydrogenases and its phosphine substituted derivatives: synthesis, electrochemistry and structural characterization.

A new cumulene diiron complex related to the Fe-only hydrogenase active site [(μ-SCH(2)C(S)CCH(2))Fe(2)(CO)(6)] (1) was obtained by treatment of (μ-LiS)(2)Fe(2)(CO)(6) with excess 1,4-dichloro-2-butyne. By controllable CO displacement of 1 with PPh(3) and bis(diphenylphosphino)methane (dppm), mono- and di-substituted complexes, namely [(μ-SCH(2)C(S)CCH(2))Fe(2)(CO)(5)L] (2: L=PPh(3); 3: L=dppm) and [(μ-SCH(2)C(S)CCH(2))Fe(2)(CO)(4)L(2)] (4: L=PPh(3); 5: L=dppm) could be prepared in moderate yields. Treatment of 1 with bis(diphenylphosphino)ethane (dppe) afforded a double butterfly complex (μ-SCH(2)C(S)CCH(2))Fe(2)(CO)(5)(μ-dppe) (7). With dppm in refluxing toluene, a dppm-bridged complex [(μ-SCH(2)C(S)CCH(2))Fe(2)(CO)(4)(μ-dppm)] (6) was obtained. These model complexes were characterized by IR, (1)H, (31)P NMR spectra and the molecular structures of 1, 2 and 5-7 were determined by single crystal X-ray analyses. The electrochemistry of 1-3 was studied and the electrocatalytic property of 1 was investigated for proton reduction in the presence of HOAc.