Reaktivität von Koordinationsverbindungen XXII [1]. Zur Kinetik der O₂‐Aufnahme von Kobalt(II)‐Chelaten 3‐zähniger Amine und Amide

Abstract

Abstract The kinetics of the interaction between molecular oxygen and the Co 2+ ‐complexes of the three terdentate ligands Z, N‐(2‐picolyl)‐ethylenediamine (PEN), N‐(2‐picolyl)‐oxamide (POA) and diethylenetriamine (DIEN) have been studied spectrophotometrically and using an O 2 specific Clark electrode. Starting from the respective 1:1‐ and 1:2‐complexes, the binuclear species ZCoO 2 (OH)CoZ and Z 2 CoO 2 CoZ 2 are formed with each ligand. The existence of the former product shows that a minimum of three chelating nitrogen donors is sufficient to make a Co 2+ ‐complex reactive towards O 2 . As derived from the empirical rate laws the same general reaction mechanism must be valid for all three systems. In the case of PEN‐ and DIEN‐complexes the oxygen adducts are metastable intermediates and formed in stoichiometric quantities. With POA irreversible formation of cobaltic species is rapid, and O 2 ‐adducts are present in steady state concentrations only, except in strongly basic solutions.