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

A series of N ‐acylated diiron azadithiolate complexes as H‐cluster models was synthesized and structurally characterized. Treatment of parent complex [{(μ‐SCH 2 ) 2 NH}Fe 2 (CO) 6 ] ( A ) with 2‐chloroacetic acid in the presence of dicyclohexylcarbodiimide or with 2‐chloroacetyl chloride in the presence of Et 3 N gave N ‐chloroacetyl complex [{(μ‐SCH 2 ) 2 NC(O)CH 2 Cl}Fe 2 (CO) 6 ] ( 1 ). Further treatment of 1 with MeC(O)SK afforded N ‐acetylthioacetyl complex [{(μ‐SCH 2 ) 2 NC(O)CH 2 SC(O)Me}Fe 2 (CO) 6 ] ( 2 ). N ‐Ethoxylcarbonylacetyl complex [{(μ‐SCH 2 ) 2 NC(O)CH 2 CO 2 Et}Fe 2 (CO) 6 ] ( 3 ) and N‐heterocyclic complexes [{(μ‐SCH 2 ) 2 NC(O)C 4 H 3 Y‐2}Fe 2 (CO) 6 ] ( 4 , Y = O; 5 , Y = S) were produced by reactions of A with EtO 2 CCH 2 C(O)Cl, 2‐furancarbonyl chloride, and 2‐thiophenecarbonyl chloride in the presence of pyridine or Et 3 N. Similarly, N ‐malonyl complex [{Fe 2 (CO) 6 (μ‐SCH 2 ) 2 NC(O)} 2 CH 2 ] ( 6 ) and N ‐carbonylbenzaldehyde complex [{(μ‐SCH 2 ) 2 NC(O)C 6 H 4 CHO‐ p }Fe 2 (CO) 6 ] ( 7 ) could be obtained by reaction of A with malonyl dichloride in the presence of pyridine and with p ‐CHOC 6 H 4 C(O)Cl in the presence of Et 3 N. More interestingly, further reaction of 7 with PhCHO and pyrrole in a 1:3:4 molar ratio in the presence of BF 3 · OEt 2 followed by p ‐chloranil yielded the first light‐driven type of model complex containing an N ‐carbonylphenylporphyrin moiety [{(μ‐SCH 2 ) 2 NC(O)(TPP)}Fe 2 (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)