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Kinetics and mechanism of formation of Cis‐diaquo‐bis‐oxalato‐chromate(III) from the mono‐oxalato complex and oxalate ions
Author(s) -
Banerjea D.,
Mohan M. S.
Publication year - 1966
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.19663470115
Subject(s) - oxalate , chemistry , chromate conversion coating , chromium , ion , aqueous solution , solvation shell , inorganic chemistry , molecule , perchlorate , kinetics , solvation , organic chemistry , physics , quantum mechanics
From spectrophotometric determination of the rate of formation of the cis‐diaquobis‐oxalato‐chromate(III) from the mono‐oxalato complex and oxalate ions in aqueous perchlorate medium (pH 2.0–5.6) and an investigation of the influence of various factors on this rate. A plausible mechanism is proposed in which the slow step is the initial one‐ended attachment of the incoming oxalate ion, by substitution of a water molecule attached to the chromium(III), followed by rapid ring closure by this oxalate, causing the displacement of another water molecule from an adjacent coordination site, forming thus the bis‐oxalato complex. This mechanism explains quantitatively the retardation by hydrogen ion and acceleration by oxalate. From the temperature dependence of the rate ΔH±(23.9 kcal/mole) and ΔS±(+8.6 e. u.) values have been evaluated by making use of the E YRING equation. The entropy of activation has been found to be positive as expected for a rate‐determining reaction between oppositely charged ions.