Cyclic tetranuclear iron-carbonyl complex containing thiobisbenzenethiolate ligands: Synthesis and structural characterization

Abstract A new macromolecular double-butterfly Fe/S carbonyl cluster, [Fe 2 (CO) 6 ] 2 ( μ -4,4′-thiobisbenzenethiolato) 2 ( 1 ), a model for the active site of [Fe-Fe] hydrogenases, has been prepared and characterized by spectroscopic methods and X-ray crystallography. The molecular structure of 1 contains two units of S 2 Fe 2 (CO) 6 covalently linked to two thiobisbenzene groups to form a 26-membered metallocycle with the benzene substituents on sulfur adopting an ae stereochemistry. The Fe-Fe bond in 1 is 2.5046(5) A which is close to that of the enzyme and related complexes. Crystals of 1 obtained from dichlormethane solution of [Fe 2 (CO) 6 ] 2 ( μ -4,4′-thiobisbenzenethiolato) 2 contain two dichloromethane molecules trapped in the cavity of 1 . Infrared spectrum of 1 has peaks at 2071, 2030, and 1972 cm −1 charateristic of the presence of the Fe 2 (CO) 6 core. Spectroscopic evidence suggest significant electronic interaction between the thiobisbenzene moieties and the S 2 Fe 2 (CO) 6 units in 1 .