CATALATIC ACTIVITY OF METAL CHELATES AND MIXED-LIGAND COMPLEXES IN NEUTRAL PH REGION .I. COPPER-IMIDAZOLE

The catalatic activity of the copper complexes of the monodentate ligand, imidazole (Im), has been investigated by means of a differential manometric technique. The kinetic data, obtained from the initial rates of O2 evolution, are consistent with a mechanism involving principally a reaction between Cu(Im)22+ and the HOO − anion. The concentrations of the catalytically active species were calculated using a computer program after taking into account the formation of 26 complexed and uncomplexed species existing in dynamic equilibrium with each other in Cu-Im-H2O2 phosphate-buffered systems. Evidence is presented for the involvement of a cupric-cuprous couple in the reaction mechanism. It is surmised that the species having two nitrogens coordinated to copper provide the lowest energy path for the reduction of the cupric ion to the cuprous ion. This presumably facilitates the rupture of the O-O bond in Im2Cu(OOH)+ because of an increase in the O-M-O bond angle in the change from the cupric to the cuprous state. © 1969, American Chemical Society. All rights reserved.