New Approach to [FeFe]‐Hydrogenase Models Using Aromatic Thioketones

Abstract

AbstractThe reactions of triiron dodecacarbonyl with thiobenzophenone (2a) and 9H‐thioxanthene‐9‐thione (2b) were investigated under different conditions. In the case of a 1:1 molar ratio of triiron dodecacarbonyl and 2a or 2b, the ortho‐metallated complexes [Fe2(CO)6{μ,κ,S,SCH(C6H5)C6H4‐η2}] (3a) and [Fe2(CO)6{μ,κ,S,SCH(C6H4)–S–C6H3‐η2}] (4a) were obtained as the major products, respectively. In contrast, the treatment of triiron dodecacarbonyl with an excess of 2a or 2b afforded [Fe2(CO)6{μ‐SCH(C6H5)C6H4S‐μ}] (3b) and [Fe2(CO)6{μ‐SCH(C6H4)–S–C6H3S‐μ}] (4b), respectively, which are both bioinspired models for the active site of [FeFe]‐hydrogenase. In addition to these complexes, the two reactions afforded [Fe2(CO)6{μ‐SC(C6H5)2S‐μ}] (3c) and [Fe2(CO)6{μ‐SC(C6H4–S–C6H4)S‐μ}] (4c). Furthermore, [{Fe2(CO)6{μ‐SCH(C6H5)2}}2(μ4‐S)] (3d) was isolated from the reaction of Fe3(CO)12 with 2a. The molecular structures of all of the new complexes were determined from the spectroscopic and analytical data and the crystal structures for 3c, 3d, 4b, and 4c were obtained. A plausible mechanism for the formation of the isolated complexes that involves dithiirane derivatives as the key intermediates is proposed. Herein, thioketones 2a and 2b act as sulfur transfer reagents. The electrochemical experiments showed that complex 3b behaves as a catalyst for the electrochemical reduction of protons from acetic acid.