Tetranuclear iron complexes bearing benzenetetrathiolate bridges as four-electron transformation templates and their electrocatalytic properties for proton reduction.
Two tetranuclear iron-sulfur complexes, (μ,μ-pbtt)[Fe(2)(CO)(6)](2) (pbtt = benzene-1,2,4,5-tetrathiolato, 3) and (μ,μ-obtt)[Fe(2)(CO)(6)](2) (obtt = benzene-1,2,3,4-tetrathiolato, 4), were prepared from  reaction of Fe(3)(CO)(12) and the corresponding tetramercaptobenzene in THF, respectively. Complexes 5 and 6, (μ,μ-pbtt)[Fe(2)(CO)(5)L(1)][Fe(2)(CO)(5)L(2)] (L(1) = CO, L(2) = PPyr(3) (Pyr = N-pyrrolyl), 5; L(1) = L(2) = PPyr(3), 6) were obtained by controlling CO displacement of 3 with PPyr(3). Molecular structures of 3-6 were determined by spectroscopic and single-crystal X-ray analyses. All-CO Fe(4)S(4) complexes 3 and 4 each display four-electron reduction processes in consecutive chemically reversible two-electron reduction events with relatively narrow potential spans in the cyclic voltammograms. Phosphine-substituted Fe(4)S(4) complexes 5 and 6 exhibit two consecutive two-electron reduction events, which are not fully reversible. The electrocatalytic properties of 3 and 4 for proton reduction were studied using a series of carboxylic acids of increasing strength (CH(3)COOH, CH(2)ClCOOH, CHCl(2)COOH, CCl(3)COOH, and CF(3)COOH). The mechanisms for electrochemical proton reduction to hydrogen catalyzed by complex 3 as a function of acid strength are discussed.
State Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology, Dalian 116024, People's Republic of China.
Lin
L
Chen
Mei
M
Wang
Frederic
F
Gloaguen
Dehua
D
Zheng
Peili
P
Zhang
Licheng
L
Sun
D001555:Benzene Derivatives / Q000737:chemistry*; D002248:Carbon Monoxide / Q000737:chemistry; D002384:Catalysis; D055664:Electrochemical Techniques; D004579:Electron Transport; D058085:Iron Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D011522:Protons
D001555:Benzene Derivatives; D058085:Iron Compounds; D011522:Protons; D002248:Carbon Monoxide