Kinetics and Mechanism of Reduction of Tris(acetylacetonato)- cobalt(III) by Hydroxylamine and Formate in Acid Media

Inorganic Chemistry Laboratories, Department of Chemistry, University College of Science,
92, Acharya Prafulla Chandra Road, Calcutta-700009, INDIA,

Manuscript received, 29 August 1977 ; accepted, 13 September 1977

The kinetics of reduction of tris(acetylacetonato)cobalt(III) by hydroxylamine and formate in aqueous acid media have been studied spectrophotometrically under different conditions. Both the complex and its protonated form are reduced by the reductants with specific rate constants k_R and K_{H. R} respectively which are concurrent to the acid catalysed self reduction of the complex. From detailed analysis of the effects of acid and reductant concentrations on the rate of reduction the specific rate constants for the different paths at different temperatures and the corresponding activation parameters have been evaluated at an ionic strength of 2M. Evidence has been presented in favour of a sort of inner-sphere mechanism of reduction involving formation of a H-bonded intermediate followed by its redox transformation by a H-atom transfer mechanism.