[Fe-Fe] hydrogenase models: Iron(I)-carbonyl clusters coupled to alpha- and para-toluenethiolate ligands
Two linkage isomers composing of diironhexacarbonyl clusters coupled to α and p-toluenethiolate ligands have been usefully prepared in moderate yields. The composition of both compounds, [(μ2-(p-toluenethiolato))2Fe2(CO)6] (1) and [(μ2-(α-toluenethiolato))2Fe2(CO)6] (2), have been determined by elemental analysis and NMR spectroscopy. A tetrairondodecacarbonyl complex, [μ4-S(μ2-(α-toluenethiolato)Fe2(CO)6)2] (3), was isolated from the reaction mixture of 2. The molecular structures of 2 and 3 determined by X-ray diffraction are discussed. An exploration of the influence of the α- and p-toluenethiolate ligands on the electronic and electrochemical properties of the iron-carbonyl units have been accomplished using infrared spectroscopy, UV-Vis spectroscopy and cyclic voltammetry. In the presence of acetic acid, compounds 1, 2 and 3 catalyze the electrochemical generation of molecular hydrogen. The proton reduction overpotentials for compounds 1 and 2 were determined to be 0.76 V and 0.85 V versus Fc/Fc+ respectively in acetonitrile as solvent. Comparatively, compound 1 produces hydrogen at an overpotential 90 mV lower than compound 2.
iron clusters, electrocatalysis, hydrogenase model, toluenethiolate, metal carbonyls
Haley, Adrian L., Lauren N. Broadbent, Lindsey S. McDaniel, Skye T. Heckman, Carlee H. Hinkle, Nikolay N. Gerasimchuk, John C. Hershberger, and Charles A. Mebi. "[Fe–Fe] hydrogenase models: Iron (I)-carbonyl clusters coupled to alpha-and para-toluenethiolate ligands." Polyhedron 114 (2016): 218-224.