Kinetic Study of the Acid-catalysed Hydrolysis of Cobalt(III) Carbonato Complexes with Nonlabile Tetrakis(methylamine), Tetrakis(ethylamine), Fac(N)-(ethylenediamine)(glycinato), Mer(N)-(ethylenediamine) (glycinato) or Bis(1,3-propanediamine) Ligands

$61.74 plus tax (Refund Policy)

Buy Article:

Abstract:

Acid-catalysed hydrolysis kinetics were studied for 14 cobalt(III) carbonato complexes involving the title five at oxonium ion concentration of 0.01-1.0 M, ionic strength of 2.0 (NaClO4) and 15-45°C (M=mol dm−3). Preprotonation constant, about 1 M−1, was estimated from a non-linear acidity dependence of an experimental rate constant for the ring-opening of the didentate hydrogencarbonato intermediate. Acidity constant, 0.003-0.7 M, and basicity constant, 0.1-0.9 M−1, of the ring-opened aquahydrogencarbonato intermediate were estimated from an acidity dependence of an experimental rate constant for the decarboxylation. Concerning the widely ranging ring-opening rate constants (0.05-126 s−1 at 25°C), we demonstrate labilizing effects of a reduced charge and of small tetrakis(amine) ligand, correlating with a high activation entropy, as well as of the trans five-membered chelate correlating with a low activation energy. The charge effect may be understood by the solvational change during the dissociative activation. Activation parameters of the uniform decarboxylation rate constant (0.2-4 s−1 at 25°C) from the aquahydrogencarbonato intermediate are higher than those of the decarboxylation from carbonic acid. This may be relevant to a Co-O bond rotation prior to the decarboxylation. The isometric structures of carbonato(ethylenediamine)(glycinato)cobalt(III) are studied by X-ray crystallography.

Keywords: Carbonato chelates; Charge effect; Cobalt(III); Hydrolysis kinetics; Stopped-flow; X-ray crystal structure

Document Type: Research Article

DOI: http://dx.doi.org/10.1080/1028662021000062608

Publication date: January 1, 2002

More about this publication?
Related content

Share Content

Access Key

Free Content
Free content
New Content
New content
Open Access Content
Open access content
Subscribed Content
Subscribed content
Free Trial Content
Free trial content
Cookie Policy
X
Cookie Policy
ingentaconnect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more