Kinetic studies on [{MFe₃S₄(SR)₃}₂(µ-SR)₃]^3–(M = Mo or W, R = Et or Ph): influence of Mo or W on the mechanism of substitution at the iron centres within the cluster

Abstract

Kinetic studies on the acid-catalysed substitution of [{MFe3S4(SR)3}2(µ-SR)3]3–(M = Mo or W, R. = Et or Ph) have shown that the heterometal influences the intimate mechanism of substitution at the iron sites. Whereas [Fe4S4(SR)4]n–(n= 2 or 3) react exclusively by a dissociative mechanism, the Mo- or W-containing clusters usually exhibit an additional associative pathway. In addition the heterometal influences the ability of the iron centres to bind a variety of small molecules. The possible relevance of these studies to the binding of substrates by certain metalloenzymes is discussed.