Methoxyphenyl‐Functionalized Diiron Azadithiolates as Models for the Active Site of Fe‐Only Hydrogenases: Synthesis, Structures, and Biomimetic H2 Evolution

A series of methoxyphenyl‐functionalized diiron azadithiolate (ADT) complexes, [{(μ‐SCH2)2N(C6H4OMe‐p)}Fe2(CO)5L] [L = CO (2); PPh3 (3); PPh2H (4)] and [{(μ‐SCH2)2N(C6H4OMe‐p)}Fe2(CO)4(CN)2][Et4N]2 (5) as the active site models of Fe‐only hydrogenases has been investigated. While model 2 was prepared in 67 % yield by a condensation reaction of N,N‐bis(chloromethyl)‐p‐methoxyaniline (1) with [(μ‐LiS)2Fe2(CO)6], models 3–5 were prepared in 49–75 % yields by a CO substitution reaction of 2 with PPh3, PPh2H, or Et4NCN, respectively. The X‐ray crystal structures of 2 and 3 revealed that the methoxyphenyl substituent is attached to the N atom by an axial bond and the nitrogen lone electron pair in an equatorial position. On the basis of cyclic voltammetric studies of 2 and 4, it was found that 2 is a catalyst for proton reduction, and an EECC mechanism is proposed for such electrocatalytic H2 production catalyzed by the ADT‐type models. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)