Associative substitution mechanisms of clusters: the relationship between sites of nucleophilic attack and leaving group dissociation

Abstract

The associative substitution mechanism of [Fe₄S₄Cl₄]^2– with 4-RC₆H₄S^– involves initial, rapid binding of the thiolate to an iron atom (Fe_a), followed by rate-limiting dissociation of a chloro-ligand; however, the origin of the leaving group changes with the electron-releasing capability of the thiolate and when R = Cl, F, H or Me, the chloro-group at Fe_a is labilised, whereas when R = Me, MeO or NH₂ the chloro-group at a remote iron site (Fe_r) is labilised.