Ormaplatin ([Pt(dach)Cl4]) represents one of the three primary structural prototypes of Pt(iv) anticancer-active prodrugs. The reduction of ormaplatin by an extended series of thiols has been studied kinetically in a broad pH range. A novel and remarkable correlation between log kRS- and the thiol dissociation constants pKRSH is disclosed: log kRS- = (0.50 ± 0.02)pKRSH + (0.68 ± 0.13), where kRS- denotes the second-order rate constant of each thiolate towards the reduction of ormaplatin.