Diiron Complexes Bearing Bridging Hydrocarbyl Ligands as Electrocatalysts for Proton Reduction

Diiron complexes with bridging hydrocarbyl ligands and Containing CO and Cp. ligands (Cp = eta(5)-C5H5) have been investigated as possible electrocatalysts for H-2 production. In particular, studies included the vinyliminium complexes [Fe-2{mu-eta(1):eta(3)-C(R')=CRC=NMe2}(mu-CO)(CO)-(Cp)(2)][SO3CF3] (R' = Tol (4-MeC6H4), 1 = H, la; R' = CH2OH, R = H, 1b; R' CH2OH, R = SPh, 1c), the vinylalkylidene [Fe-2{mu-eta(1):eta(3)-C(Tol) CH=CHNMe2} (mu-CO) (CO) (CP)(2)], the amino alkylidyne [Fe-2{mu-CN(Me)(R)}(mu-CO)(CO)(L)(CP)(2)}[SO3CF3]: (R = Me, L = CO, 3a; R = Me, L = NCMe, 3h; R = Xyl (2,6-Me2C6H3), L = 'CO, 3c), [Fe-2{mu-CN(Me)(2)}(mu-L')(CO)(L)(Cp)(2)] (L' = CO, L = CN, 4; L' = H, L = CO, 5), the thiocarbyne complexes [Fe-2(mu-CSEt)(mu-CO)(CO)(2)(CP)(2)][BF4], (6) and [Fe-2(mu-CSMe)(mu-CO)(CO)(CN)(Cp)(2)] (7), and the.alkylidene complexes [Fe-2{mu-C(CN)(SMe)}(mu-CO)(CO)(2)(CP)(2)[SO3CF3] (8) and [Fe-2{mu-C(CN)(PMe2Ph)}(mu-CO(CO)(2)(CP)(2)][SO3CF3] (9). Cyclic voltammograms (CV) of the above complexes in CH3CN have been recorded in the presence of increasing amounts of acetic acid to evidence electrocatalytic proton reduction. In spite of the fact that the above di_iron complexes do not resemble the typical diiron dithiolate toodel systems, the aminocarbyne 4 and the thiocarhyne complex 7 exhibit significant electrocatalytic properties for proton reduction (e.g., for 4, the turnover number (TON) is 15.5).