Axial ligand dissociation of phthalocyaninatoiron(II) adducts; further evidence for a dissociative mechanism of substitution

Abstract

The kinetics of reaction of [Fe(pc)L₂](pc = phthalocyaninate, L = imidazole or 4-aminopyridine) with dimethyl sulphoxide have been studied over the range 20–45 °C. The rate-determining step is loss of the first ligand. Dilution with acetone or benzene enhances the observed first-order rate constant such that it is proportional to the reciprocal of the concentration of dmso over the range 1–14 mol dm^–3. This is shown to be consistent with a D mechanism and some rate constants for the individual steps are derived. A comparison of trans effects at the phthalocyaninatoiron(II) centre is made.