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Mechanistic Studies on the reactions of cis‐diaquobisoxalatochromate(III) ion with 2,2′‐dipyridyl and 1,10‐phenanthroline
Published in -
Volume: 399
Issue: 1
Pages: 115 - 119
Kinetic studies in aqueous solutions on the replacement of the aquo ligands in cis‐Cr(Ox)2(H2O) 2− by 2,2′‐dipyridyl (dipy) and 1,10‐phenanthroline (phen) forming cis‐Cr(Ox)2(AA)− (AA = dipy or phen) were made spectrophotometrically. The reaction in each case occured in two concurrent paths, one of which was independent of the reagent (AA) concentration (rate constant, k0, identical for both the systems), and another which was first order with respect to it (rate constant, kR). k0 and kR values have been evaluated at different temperatures (40–70°C), and from there the corresponding ΔH≠ and ΔS≠ values. The results suggest a dissociation mechanism for the reagent independent path where CrOH2 bond rupture is only significant in the transition state. The value of kR/k0 (higher for phen compared to dipy) was of the order of 102 suggesting significant bond formation by the reagent in the transition state of the reagent dependent path. However, ΔH≠ corresponding to kR was ca. 1.7 to 1.8 times that corresponding to k0 indicating that in the reagent dependent path simultaneous rupture of the two CrOH2 bonds in cis positions occur as expected from steric considerations for these bidendate ligands. Increase in ionic strength of the of the medium causes a slight acceleration of the reagent‐dependent path only. Copyright © 1973 Verlag GmbH & Co. KGaA, Weinheim
About the journal
JournalZAAC ‐ Journal of Inorganic and General Chemistry