title: Diiron proton reduction catalysts possessing electron-rich and electron-poor naphthalene-1,8-dithiolate ligands.
abstract: The diiron complexes [Fe(2)(CO)(6)(1,8-S(2)-2,4,5,7-Cl(4)C(10)H(2))] (3), [Fe(2)(CO)(6)(1,8-S(2)C(10)H(6))] (4), and [Fe(2)(CO)(6)(1,8-S(2)-2,7-tBu(2)C(10)H(4))] (5) were synthesized in moderate yield from naphthalene-1,8-dithiols and [Fe(3)(CO)(12)]. They were characterized by IR, (1)H and (13)C NMR spectroscopy and 3 and 4 were characterized by X-ray crystallography. They contain a butterfly Fe(2)S(2) core with Fe-Fe distances of 2.529(1) (3) and 2.506(1) A (4). Cyclic voltammetry (CH(2)Cl(2)/nBu(4)PF(6)) revealed two one-electron reductions, at potentials more positive than those for the related [Fe(2)(CO)(6)(S(CH(2))(3)S)] (1), and one one-electron oxidation. The first reduction of the electron poor 3 (-1.60 V vs Fc/Fc(+)) is 240 mV more positive than the first reduction of the electron rich 5 (-1.84 V). Electrochemical studies revealed that 3-5 facilitate the proton reduction of p-toluenesulfonic acid. The rates of catalysis, with a 95% confidence limit, are 2.4+/-0.8 (1), 5.2+/-0.8 (3), 3.1+/-1.1 (4), 2.9+/-0.6 (5), and 4.5+/-0.2 h(-1) for the related [Fe(2)(CO)(6)(1,2-S(2)C(6)H(4))]. The rates were determined by bulk electrolysis at -1.70 V (Fc/Fc(+)), which correspond to an overpotential of 1.05 V for p-toluenesulfonic acid.
authors: Department of Chemistry, University of California, Berkeley, CA 94720 (USA), Fax: (+1) 510-642-8940.
authors: Robert J
authors: RJ
authors: Wright
authors: Department of Chemistry, University of California, Berkeley, CA 94720 (USA), Fax: (+1) 510-642-8940.
authors: Christopher
authors: C
authors: Lim
authors: Department of Chemistry, University of California, Berkeley, CA 94720 (USA), Fax: (+1) 510-642-8940.
authors: T Don
authors: TD
authors: Tilley
mesh_terms: D002384:Catalysis; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D005290:Ferric Compounds / Q000737:chemistry*; D006864:Hydrogenase / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D009281:Naphthalenes / Q000737:chemistry*; D010084:Oxidation-Reduction; D011522:Protons; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D007506:Iron-Sulfur Proteins; D008024:Ligands; D009281:Naphthalenes; D011522:Protons; D013438:Sulfhydryl Compounds; C545034:naphthalene-1,8-dithiolate; C118830:iron hydrogenase; D006864:Hydrogenase