Ligands containing elements of Group VIB. Part III. The silver complexes of saturated and unsaturated (alkylthio)acetic and p-(alkylthio)benzoic acids

Abstract

A range of (alkylthio)acetic and p-(alkylthio)benzoic acids of general formula RSCH₂·CO₂H and p-RS·C₆H₄·CO₂H(HL) where R is Me, Et, Prⁿ, Bu⁸, Buⁿ, n-C₅H₁₁, n-C₆H₁₃, PhCH₂, Ph, CH₂:CH·CH₂, CH₂:CH·(CH₂)₂, and CH₂:CH(CH₂)₃, has been prepared and the acid dissociation constants of the acetic acids measured at 25° and µ= 0·10M(KNO₃). The formation constants of the silver complexes, AgL (µ= 0·1 or 0·2M), of all the ligands and of the protonated silver complexes, AgHL(µ= 0·20M), of the acetic acids have been measured in acetate buffer solutions at 25°. Stabilities vary with the inductive effects of the substituents (as expressed by Taft σ* functions) suggesting that changes in σ-bonding between sulphur and silver atoms are the major factor contributing towards the free-energy changes found. As would be expected from this assumption, bonding of phenyl groups to the sulphur atom markedly reduces the stabilities of the complexes. The olefinic bond in the unsaturated ligands co-ordinates strongly when the substituent is but-1-enyl, weakly with pent-1-enyl, and negligibly with the allyl group.