Synthesis and Cluster Interconversion Chemistry of a Linear Trinuclear Hexakis(µ-benzenethiolato)triiron(II) Hexacarbonyl Compound

The neutral compound (1) assembles in a solution containing NaSPh and FeCl₂in a 2:1 ratio in ethanol under an atmosphere of carbon monoxide at room temperature. It also forms in the reaction of the ion with CO and FeBr₂ and by the oxidative addition of PhSSPh to an Fe(0) carbonyl species with UV irradiation in an inert atmosphere under ambient conditions. Product was characterized by X-ray diffraction and found to be a linear trinuclear complex in which the benzenethiolate ligands occupy bridging positions and the carbonyl ligands are exclusively terminally bonded. Crystal data are space group with a = 11.077 (1) A, b = 10.488 (1) A, c = 19.052 (2) A, ß= 95.41 (6)°, V = 2203.52 A³, and Z = 2. On the basis of the observed octahedral coordination of each of the iron atoms in 1, it is suggested that octahedral coordination may occur in the limit of unrestricted CO binding in the CO-inhibited states of iron-sulfur enzymes. Compound 1 converts to (2) in neat Me₂SO solution where the counterion is probably The Compound [Fe₄(SPh)₁₀] (3) is formed in a mixed solution of Me₂SO/THF (1:25, v/v) and can be isolated as brown crystals. The self-assembly of these clusters in lieu of others that could form with the same Fe:thiolate ratio suggests that those which are obtained represent clusters with particularly stable structures. The formation of clusters in such “stoichiometrically free” environments suggests new approaches to the study of cluster formation.