Violurato complexes of nickel(II). Formation equilibria. Deprotonation equilibria of the coordinated ligands and related stereochemical changes

Summary The formation equilibria of nickel(II) violurato-complexes in water and dimethylsulphoxide-water (8020) as well as deprotonation of the coordinated ligands and related stereochemical changes are reported. The stability constants of the Ni²⁺-H₂V^– complexes log₁=5.06, Iog₂=9.38, log₃=12.98 as well as the acidity constants of the Ni(H₂V)₃]^– complex, log_j1= 8.37, log_j2=15.76, log_j3=22.37 are determined at 25 °C and 0.1M NaClO₄. A new violurato-complex of Ni²⁺, Na₄Ni(HV)₃]5H₂O, is isolated and characterized.