Equilibria in complexes of N-heterocyclic molecules. Part 8. Reaction of tris(5-nitro-1,10-phenanthroline)ruthenium(II) cation with methoxide and ethoxide ions

Abstract

Spectroscopic studies show that methoxide ion reacts reversibly with methanolic solutions of the tris(5-nitro-1,10-phenanthroline)ruthenium(II) cation, [RuL₃]²⁺, via addition to the 2 position of each heterocyclic ligand. An analogous addition occurs with ethoxide ion in ethanol, except that with excess of [OEt]^– the diethoxy-adduct is precipitated. The kinetics of addition of the first alkoxide ion have been examined in both cases. With methoxide ion the observed rate law, Rate =k₁[Ru][OMe^–]+k_–1[Ru], allows evaluation of both forward and reverse rate constants. For ethoxide ion a simple second-order rate law, Rate =k₁[Ru][OEt^–], is observed. Comparison with similar data for the related additions of [OH]^– and [CN]^– ions to [RuL₃]²⁺ shows the relative rate order [OEt]^– > [OMe]^–[OH]^–[CN]^–.