Octahedral cobalt(III) complexes in dipolar aprotic solvents. III. A new spectrophotometric method for the determination of ion association constants

Abstract

A spectrophotometric method for the evaluation of ion association constants has been developed. This method involves the preparation of solutions containing only the compound under consideration. A function relating the association constants to the concentration of compound and extinction coefficients has been derived. The association constants are best determined by an iterative method using a computer. The association constant for the cis-diohlorobisethylenediaminecobalt(111) cation, cis-[Co en2 Cl2]+, and chloride ion in NN-dimethylformamide (DMF) at 30� has been calculated by this new method and is compared with that of another established procedure. The association constant has also been determined for the association of cis-[Co en2 Cl2]+ and iodide in DMF at 30�.

Solvation of ions. XXIII. Enthalpies of transfer of some divalent metal ions from water to nonaqueous solvents

“…26 Ion association constants for di-univalent electrolytes in the dipolar aprotic solvents are scarce but perchlorates are strong electrolytes at 10-3 M whenever studied. 27 The KA of L1CIO4 in CH3CN,28 a solvent in which ion association is likely to be more significant than others, is only 4, suggesting that KA for the di-univalent electrolytes studied is less than 50 and thus that ion-association effects are not sigificant at <3 X 10-3 M.…”