The N‐Acylated Derivatives of Parent Complex [{(μ‐SCH2)2NH}Fe2(CO)6] as Active Site Models of Fe‐Only Hydrogenases: Synthesis, Characterization, and Related Properties

Abstract

AbstractA series of N‐acylated diiron azadithiolate complexes as H‐cluster models was synthesized and structurally characterized. Treatment of parent complex [{(μ‐SCH2)2NH}Fe2(CO)6] (A) with 2‐chloroacetic acid in the presence of dicyclohexylcarbodiimide or with 2‐chloroacetyl chloride in the presence of Et3N gave N‐chloroacetyl complex [{(μ‐SCH2)2NC(O)CH2Cl}Fe2(CO)6] (1). Further treatment of 1 with MeC(O)SK afforded N‐acetylthioacetyl complex [{(μ‐SCH2)2NC(O)CH2SC(O)Me}Fe2(CO)6] (2). N‐Ethoxylcarbonylacetyl complex [{(μ‐SCH2)2NC(O)CH2CO2Et}Fe2(CO)6] (3) and N‐heterocyclic complexes [{(μ‐SCH2)2NC(O)C4H3Y‐2}Fe2(CO)6] (4, Y = O; 5, Y = S) were produced by reactions of A with EtO2CCH2C(O)Cl, 2‐furancarbonyl chloride, and 2‐thiophenecarbonyl chloride in the presence of pyridine or Et3N. Similarly, N‐malonyl complex [{Fe2(CO)6(μ‐SCH2)2NC(O)}2CH2] (6) and N‐carbonylbenzaldehyde complex [{(μ‐SCH2)2NC(O)C6H4CHO‐p}Fe2(CO)6] (7) could be obtained by reaction of A with malonyl dichloride in the presence of pyridine and with p‐CHOC6H4C(O)Cl in the presence of Et3N. More interestingly, further reaction of 7 with PhCHO and pyrrole in a 1:3:4 molar ratio in the presence of BF3·OEt2 followed by p‐chloranil yielded the first light‐driven type of model complex containing an N‐carbonylphenylporphyrin moiety [{(μ‐SCH2)2NC(O)(TPP)}Fe2(CO)6] (8, TPP = tetraphenylporphyrin group). Whereas the molecular structures of 2, 5, and 7 were established by X‐ray crystallography, the electrochemical properties of 2–5 as well as the proton reduction to hydrogen gas catalyzed by 2 and 3 were studied by CV techniques.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)