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-SCH2C(S)CCH2)Fe2(CO)6] (1) was obtained by treatment of (μ-LiS)2Fe2(CO)6 with excess 1,4-dichloro-2-butyne. By controllable CO displacement of 1 with PPh3 and bis(diphenylphosphino)methane (dppm), mono- and di-substituted complexes, namely [(μ-SCH2C(S)CCH2)Fe2(CO)5L] (2: L = PPh3; 3: L = dppm) and [(μ-SCH2C(S)CCH2)Fe2(CO)4L2] (4: L = PPh3; 5: L = dppm) could be prepared in moderate yields. Treatment of 1 with bis(diphenylphosphino)ethane (dppe) afforded a double butterfly complex [(μ-SCH2C(S)CCH2)Fe2(CO)5]2(μ-dppe) (7). With dppm in refluxing toluene, a dppm-bridged complex [(μ-SCH2C(S)CCH2)Fe2(CO)4(μ-dppm)] (6) was obtained. These model complexes were characterized by IR, 1H, 31P 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.

Graphical abstractA new diiron complex [(μ-SCH2C(S)CCH2)Fe2(CO)6] (1) and its phosphine-substituted derivatives related to the active site of Fe-Hases have been synthesized. The biomimetic H2 evolution catalyzed by 1 was also investigated.Figure optionsDownload full-size imageDownload as PowerPoint slide