Equilibrium and kinetic study of the reaction between phthalocyaninatoiron(II) and carbon monoxide in dimethyl sulphoxide

Abstract

The reaction between carbon monoxide and phthalocyaninatoiron(II) in dimethyl sulphoxide (dmso) has been studied kinetically and from the equilibrium point of view. In the presence of a large excess of CO, the iron complex adds carbon monoxide in a 1:1 mole ratio via pseudo-first-order kinetics. The observed rate constant has the form k_obs.=k_f[CO]+k_r with k_f= 1.28 ± 0.05 × 10³ dm³ mol^–1 s^–1 and k_r= 0.12 ± 0.02 s^–1 at 20 °C. The equilibrium constant K is close to 1 × 10⁴ dm³ mol^–1 and is virtually independent of temperature. The effect of temperature on the rate constants has been investigated and the activation parameters determined; their mechanistic implications are discussed.