Unexpected explanation for the enigmatic acid-catalysed reactivity of [Fe_4S_4X_4]~(2-) clusters

摘要

Density functional calculations show that Fe-S clusters undergo unexpected large structural changes when protonated at S. Proton-ation of prototypical cubanoid [Fe_4S_4X_4]~(2-) to [Fe_4S_3(SH)X_4]~- (X = Cl, SR, OR) results in formation of doubly-bridging SH, severance of one Fe-S bond, and creation of a three-coordinate Fe. These findings explain previously enigmatic results concerning the reactivity of these clusters, including the rates of protonation, pK_a data, and the kinetics of acid-catalysed ligand substitution.