Solvation and reactivity of tris(diimine)–iron(II) complexes in aqueous ethane-1,2-diol, propane-1,2,3-triol and sucrose

Abstract

The dependence of rate constants for base hydrolysis on solvent composition for several iron(II)–diimine complexes has been established for aqueous ethane-1,2-diol (ethylene glycol) and aqueous propane-1,2,3-triol (glycerol) mixtures, and for aqueous sucrose solutions. These dependences are compared with analogous reactivity trends for binary aqueous solvent mixtures containing monohydroxylic alcohols. Transfer chemical potentials for iron(II)–diimine complexes, and for simple cations and anions, have been estimated on the TATB assumption for transfer to aqueous ethane-1,2-diol and aqueous propane-1,2,3-triol. These transfer chemical potentials allow resolution of the observed reactivity trends into initial-state and transition-state contributions for the aqueous ethane-1,2-diol mixtures. Such information on the role of solvation in this type of reaction is complented by the determination of activation volumes for base hydrolysis for four iron(II)–diimine complexes in aqueous ethane-1,2-diol.