DISSOCIATION KINETICS OF [FE(PHEN)3]2+, [FE(BIPY)3]2+ AND [FE(4,4'-ME2BIPY)3]2+ IN THE PRESENCE OF CYANIDE ION IN AQUEOUS-SOLUTION AT PRESSURES UP TO 1 KILOBAR

Rate constants for dissociation, in aqueous solution at 25-degrees-C, of [Fe(phen)3]2+, [Fe(bipy)3]2+, and [Fe(4,4'-Me2bipy)3]2+ in the presence of cyanide, and of the last-named complex also in the presence of hydroxide, are significantly decreased by the application of pressure (up to 1 kbar). Kinetic measurements were carried out using a high pressure cell of improved design to that used in our earlier investigations. Volumes of activation, DELTAV*, are scarcely sensitive to ligand or to attacking nucleophile, being in the range of 10-12 cm3 mol-1. An explanation of these results resides in an associative mechanism, a scheme invoked for similar reactions reported previously.