Mechanisms of substitution reactions of octahedral bis(ditertiaryarsine) complexes. Part III. Effect of acidity upon the isomerisation, chloride exchange, and thiocyanate substitution of cis-dichlorobis-(o-phenylenebisdimethylarsine)cobalt(III) perchlorate in methanol

Abstract

The effect of acidity on the isomerisation, [³⁶Cl]chloride exchange, and thiocyanate substitution of cis-dichlorobis-(o-phenylenebisdimethylarsine)cobalt(III) perchlorate in methanol has been studied and is reported. The cis-isomer converts to trans in acid solutions without ionisation of the co-ordinated chloride, suggesting an intra-molecular isomerisation mechanism. Substitution, isotopic exchange, and also isomerisation are observed when no acid is added to the reaction mixtures. It is suggested that both isotopic exchange and substitution involve the formation of an acid-sensitive intermediate.