Methoxyphenyl‐Functionalized Diiron Azadithiolates as Models for the Active Site of Fe‐Only Hydrogenases: Synthesis, Structures, and Biomimetic H 2 Evolution

A series of methoxyphenyl‐functionalized diiron azadithiolate (ADT) complexes, [{(μ‐SCH 2 ) 2 N(C 6 H 4 OMe‐ p )}Fe 2 (CO) 5 L] [L = CO ( 2 ); PPh 3 ( 3 ); PPh 2 H ( 4 )] and [{(μ‐SCH 2 ) 2 N(C 6 H 4 OMe‐ p )}Fe 2 (CO) 4 (CN) 2 ][Et 4 N] 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) 2 Fe 2 (CO) 6 ], models 3 – 5 were prepared in 49–75 % yields by a CO substitution reaction of 2 with PPh 3 , PPh 2 H, or Et 4 NCN, 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 H 2 production catalyzed by the ADT‐type models. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)