Stability, spectra and structure of the cobalt(II) chloride complexes in hexamethylphosphoramide solution at 25°C

Abstract

Cobalt(II) chloride complexes were investigated spectrophotometrically in hexamethylphosphoramide (HMPA) solutions. It has been established that four consecutive tetrahedral chloro complexes of cobalt(II) are formed in the Co(ClO4)2-CoCl2 and CoCl2-LiCl-HMPA solutions. The formation constants of the complexes have been calculated: log K1 = 9.0 (±0.5), log K2 = 6.5 (±0.5), log K3 = 3.05 (±0.05) and log K4 = − 1.42 (±0.03). The high stability of the dichloro-complex results in the fact that this species is the only complex of cobalt(II) existing in HMPA solutions of CoCl2.