Co-ordination of silver(I) to olefinic bonds. Complex formation between cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), and silver(I) and some unsaturated derivatives of acetic and iminodiacetic acids

Abstract

A number of substituted malonic, RCH(CO₂H)₂, acetic, RCH₂CO₂H, and iminodiacetic acids, RN(CH₂CO₂H)₂. containing substituent groups incorporating olefinic bonds have been synthesised (R = CH₂:CH·CH₂, CH₂:CH·CH₂·CH₂, and CH₂:CH·CH₂·CH₂·CH₂) and the formation constants of their complexes with H⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Ag⁺ measured at 25 °C and I= 0·10M. Chelate formation takes place between the Ag⁺ ion and the ligands able to form chelate rings which are ‘four-and-a-half’ membered or larger. There is no evidence for chelate formation with the other metal ions studied. Potentiometric measurements over a range of temperatures show formation of the Ag⁺–allylacetate mono complex to be the result of a large favourable enthalpy change (–17·5 kJ mol^–1) opposed by the entropy change (TΔS=–6·0 kJ mol^–1 at 25 °C).