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Effect of solvent on the reactions of coordination complexes: Part 16. Kinetics and mechanism of complexation of oxalatopentaammine‐cobalt(III) with nickel(II) in methanol‐water medium
Author(s) -
Dash Anadi C.,
Pradhan Jyotshamayee
Publication year - 1992
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550240204
Subject(s) - chemistry , nickel , cobalt , dissociation (chemistry) , solvent , carboxylate , kinetics , moiety , inorganic chemistry , rate determining step , oxalate , reaction rate constant , solvent effects , medicinal chemistry , stereochemistry , organic chemistry , catalysis , physics , quantum mechanics
The kinetics of reversible complexation of oxalatopentaammine cobalt(III) with Ni 2+ has been investigated in MeOH + water media (0–50 (v/v) % MeOH) at 15.0–35.0°C and I = 0.10 mol dm −3 . Analysis of rate data indicates that the monobonded complex [(NH 3 ) 5 · CoOCOCO 2 Ni] 3+ in which Ni 2+ is bound to the end carboxylate group is the possible reaction intermediate. The formation and dissociation rates of such a species are rate limiting for the overall formation and dissociation of the binuclear species, in which Ni 2+ is chelated by the oxalate moiety. The rate and activation parameters for formation and dissociation of the binuclear species are moderately solvent sensitive and solvent structural effects are discernible in the nonlinear variations of Δ H ≠ and Δ S ≠ with solvent composition. The log k r vs. Grunwald Winstein parameter (Y Bu t Cl ) plot for the dissociation of the binuclear species is markedly nonlinear.