Base Hydrolysis Kinetics of Cobalt(III) Spiro-Octaamine Dimer


Abstract: The preparation and characterisation of a cobalt (III) complex of octaaza ligand, 5, 5'-bis(4-amino-2-azabutyl)-1,9-diamino-3,7-diazanonane (octaam) is described. The base hydrolysis kinetics of bis cobalt(III) of octaam has been studied spectrophotometrically by the stopped-flow technique. A consequent reaction is observed in the base hydrolysis of the spiro-octaamine with the fast reaction having k_{OH} = 3.55 M^{-1}s^{-1} and the slower reaction k_{OH} = 0.72 M^{-1}s^-1} at 298 K with \Delta H^{\#} = 89 kJ/mol for the fast stage and \Delta H^{\#} = 102 kJ/mol for the slow stage (I = 0.4 M NaClO_4). The fast reaction is assigned to the hydrolysis of the trans diaqua and the slower to further hydrolysis of the remaining Cl ions. The reaction appears to proceed predominantly by a D_{CB} (dissociative conjugate base) mechanism.


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