Kinetics of aquation of bis(2,2′;6′,2″-terpyridyl)iron(II) in acidic media and its reaction with cyanide ion

Abstract

The kinetics of aquation of bis(2,2′;6′,2″-terpyridyl)iron(II), [Fe(terpy)₂]²⁺, have been examined in aqueous solution, and a mechanism consistent with the observed pH–rate profile proposed. Activation parameters for fission of the first iron–nitrogen bond have been determined and compared with those for related complexes. The rate law for reaction of [Fe(terpy)₂]²⁺ with cyanide ion is as in equation (i). Activation parameters for the –d[Fe(terpy)₂ ²⁺]/dt=k₉+k₁₀[CN^–][Fe(terpy)₂ ²⁺](i), k₁₀ path, which is the dominant reaction route, are compared with those for analogous second-order reactions of similar iron(II) complexes with cyanide ion. Solvatochromic behaviour is reported for the [Fe(terpy)(CN)₃]^– anion, the primary product of the reaction of [Fe(terpy)₂]²⁺ with cyanide.