Kinetics of Incorporation of Zinc (II) into Tetraphenylporphine in N,N-Dimethylformamide. I. Monohydroxo and Acetato Complexes

The kinetics of incorporation of zinc(II) into meso-tetraphenylporphine in N,N-dimethylformamide (DMF), at 30°, were affected by the trace water in the solvent and by the presence of acetate ion (OAc^-). The reaction was one half order in Zn(GlO_4,2 • 6H₂O, whereas first order in Zn(ClO_4,2·6DMF. Addition of HClO₄ to the water containing system retarded the reaction rate and converted the kinetics to the first order with respect to total Zn(II). The main path for the reaction of Zn(ClO_4,2·6H₂O was concluded to be that involving the monohydroxo species, Zn(OH)⁺ Addition of acetate anion increased the rate, until at a ratio [OAc^-]/[Zn] of unity the rate reached a maximum; an increase of the ratio past unity caused a rate decrease. The species, Zn(OAc)⁺, is concluded to be more reactive than the fully solvated Zn(II) species and Zn(OAc)₂.