Ionization equilibria in solutions of cobalt(II) thiocyanate in N,N-dimethylformamide

Abstract

Visible absorption spectra and the molar conductance curve for Co(NCS)₂ in N,N-dimethylformamide (DMF), together with the spectra for the Co(ClO₄)₂–KNCS–DMF, Co(NCS)₂–KNCS–DMF and Co(NCS)₂–DMF–chlorobenzene systems, have been determined at 25 °C. The results indicate the formation of the CoNCS(DMF)⁺₅ and Co(NCS)^2–₄ complexes in the Co²⁺–NCS^––DMF systems. The stability constants are given by log β₁= 4.5 ± 0.1 and log β₄= 12.2 ± 0.3. The high stability of the tetrahedral Co(NCS)^2–₄ complex leads to the formation of 2CoNCS(DMF)⁺₅·Co(NCS)^2–₄ complex electrolytes in the most concentrated solutions of Co(NCS)₂ in DMF.