VOLUMES OF ACTIVATION FOR DISSOCIATION OF THE CATIONS OF [TRIS-2,2'-BIPYRIDYL]IRON(II), [TRIS-1,10-PHENANTHROLINE]IRON(II) AND OF OTHER DIIMINE IRON(II) COMPLEXES IN AQUEOUS-SOLUTION

The kinetics of dissociation of several iron(II) diimine complexes by aqueous hydroxide ions have been studied spectrophotometrically at atmospheric pressure and elevated pressures, at 298.2 K. Values of DELTA-V* are between + 10 and + 16 cm3 mol-1, and are interpreted as arising from a significant loss of electrostricted water from the hydroxide ion as it reacts with the iron(II) complex associatively. Dissociation of the [Fe(5NO2phen)3]2+ and [Fe(5Brphen)3]2+ complexes in the presence of aqueous EDTA is reported. For both, DELTA-V* is + 22 cm3 mol-1. These values can be understood by considering the reaction as a process comparable to aquation in acidic medium, a dissociative process. Activation enthalpy data support this idea.