SOLVATION AND REACTIVITY OF THE LOW-SPIN TRIS-DIIMINE IRON(II) COMPLEX OF THE SCHIFF-BASE LIGAND DERIVED FROM 2-BENZOYLPYRIDINE AND 3,4-DIMETHYLANILINE, [FE(ME2BSB)3]2+

The reactivity and solvation of the iron(II) tris complex made from the bidentate ligand obtained by condensing phenyl 2-pyridyl ketone and 3,4-dimethylaniline have been examined in aqueous solution and in aqueous solvent mixtures. Base hydrolysis kinetics measurements upon the complex ion, [Fe(Me2bsb)3]2+, show an increasing rate of dissociation with increasing co-solvent concentration, due largely to the destabilization of the hydroxide ion. The predicted preference the lipophilic complex would exhibit toward solvents less polar than water is an expectation that is realized when transfer (from water to aqueous solvent mixtures) chemical potential trends are analysed. The latter parameters were obtained from solubility measurements. When corresponding transfer chemical potentials for the transition state are also considered, the factors controlling reactivity patterns are shown; this is described by an initial state-transition state analysis. Base hydrolysis kinetics carried out at high pressures (up to 1 kbar) yield the volumes of activation, DELTAV*, which provide a complementary view of solvation. Some measurements with a similar complex, [Fe(Me2tsb)2]2+, are reported for comparison.