Synthesis, structures, and properties of diiron azadithiolate complexes containing a subphthalocyanine moiety as biomimetic models for [FeFe]-hydrogenases

Article abstract of DOI:10.1002/ejic.201300038

The first two model compounds for [FeFe]-hydrogenases that contain a subphthalocyanine (SubPc) macrocycle, namely, [{(μ-SCH₂) ₂N(CH₂)₂CO₂-3-C₆H ₄S₂C₆H₄-3′-O(SubPc)}Fe ₂(CO)₆] (5) and [{(μ-SCH₂) ₂NC₆H₄-4-O(SubPc)}Fe₂(CO) ₆] (8), have been synthesized and structurally characterized. The treatment of chlorosubphthalocyanine (SubPc-Cl, 1) with (3-HOC₆H ₄S)₂ in toluene gave the corresponding phenoxy-substituted SubPc derivative 3-HOC₆H₄S₂C₆H ₄-3′-O(SubPc) (2) in 78 % yield, whereas the reaction of in-situ-generated [(μ-HOCH₂S)₂Fe₂(CO) ₆] (3) with β-alanine afforded diiron complex [{(μ-CH ₂S)₂N(CH₂)₂CO₂H}Fe ₂(CO)₆] (4) in 53 % yield. Further treatment of 2 with 4 in the presence of N,N′-dicyclocarbodiimide (DCC) and N,N-dimethyl-4- aminopyridine (DMAP) in CH₂Cl₂ resulted in the formation of model compound 5 in 86 % yield. Model compound 8 could be prepared by two methods. One method involves the reaction of in-situ-generated 3 with 4-aminophenol in tetrahydrofuran (THF) to give diiron complex [{(μ-CH ₂S)₂NC₆H₄OH-4}Fe₂(CO) ₆] (6) in 61 % yield and further treatment of SubPc-Cl (1) with 6 in toluene to give 8 in 13 % yield. The other method involves the reaction of SubPc-Cl (1) with silver triflate (AgOTf) followed by treatment of the resulting intermediate SubPc-OTf (7) with 6 in the presence of Et₃N to produce 8 in a much higher yield (59 %). All the new precursors (2, 4, and 6) and the model compounds 5 and 8 have been fully characterized by elemental analysis and various spectroscopy techniques, as well by X-ray crystallography for 2, 4, 6, and 8. In addition, the photoinduced H₂ production catalyzed by model 8 was preliminarily investigated. Copyright