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.