Influence of ligand-water interactions on the aquation of pentacyano (saturated amine) ferrate (ll) ions

Abstract

Rate constants and activation parameters for the aquation of I 2 saturated amines from penlacyanoamineferrate(II) in I M pyridiné solutions are reported. While ΔG values do not correlate with ΔG° (for the ionization of the conjúgate acid) or with a* and E„ Taft’s constants, an isokinetic relationship is found. For the series (CH3) NH3 and RNH 2, ΔH2 correlates with ΔH° in water and cach series shows an independent correlation of ΔS° with ΔS°. These results are interpreted in terms of an adapted Caldin and Bcnetto’s model for Exchange reactions, the main contribution to the changes in activation parameters arising.seemingly from the energetics of transfer of the released ligand to bulk water. This small contribution to the activation process in water is rendered observable by the remarkable insensitivity of the rate process to “ inner” bonding effects.