Energy Value of the Octahedral-Tetrahedral Coordination Change
- 1 August 1961
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 35 (2), 467-472
- https://doi.org/10.1063/1.1731954
Abstract
The equilibrium oct(CoCl2Py4) = tet(CoCl2Py2) +2Py for cobaltous chloride solutions in pyridine is followed over a temperature range, yielding ΔH = +13.4 kcal/mole. At 38°C the equilibrium constant is estimated as (CoPy2Cl2) (Py)2/(CoCl2Py4) = 0.04, and the ΔS for the reaction is about 36.7 eu. It is pointed out that the average bond strength in the tetrahedral species is about 17 kcal greater than for the same groups in the octahedral configuration, and that the strength of binding and the dissociation energy for the two ligands released according to the equation above are significant factors in determining the equilibrium reaction. Detailed arguments are given against the view that the relative stability of octahedrally and tetrahedrally coordinated complexes, such as the pair discussed, reflect principally the difference in ``ligand‐field stabilization'' of the nonbonding d electrons between octahedral and tetrahedral fields.Keywords
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