Coordination states of Co(NCS)2 and Ni(NCS)2 in dimethyl sulphoxide

Abstract

Visible absorption spectra and the molar conductance curves for Co(NCS)₂ and Ni(NCS)₂ have been determined at 25 °C. The results indicate the formation of the mono- di-and tetra-thiocyanate complexes of cobalt(II) in the Co²⁺–NCS^––DMSO systems, while the mono-, and di-thiocyanate species are present in the Ni²⁺–NCS^––DMSO solutions. The stability constants of the cobalt(II) complexes are given by logβ₁= 2.85 ± 0.07, logβ₂= 4.59 ± 0.14 and logβ₄= 6.83 ± 0.05. The respective values for the nickel(II) complexes are logβ₁= 3.01 ± 0.03 and logβ₂= 4.77 ± 0.11