ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Cyanatocuprate(II) complexes in methanol

M. Quastlerová and Z and Valtr

Department of Inorganic Chemistry, Slovak Technical University, Bratislava

Abstract: Investigating spectrophotometrically the methanol solutions of Cu(Cl0₄)₂ and of KOCN, formation of relatively stable cyanatocuprate(II) complex was found. The emerald green solutions which are formed in reaction of/Cu(Cl0₄)₂. 6H₂0 with KOCN, have no absorption maximum in the visible range, but they have a well denned maximum in the ultraviolet region at 300 nm. The character of the absorption curves does not change with the- concentration (in the range 1 . 10^-4 — 2.5 . 10^-3 м). By the Job's method and by the method of monovariant changes the formation of the complex at the ratio of Cu²⁺ : OCN^- = 1 : 1.5 was detected. In the infrared range, this complex yields a new absorption band at the wavelength 2240 cm^-1 ; when there is excess of OCN^- in the solution (e. g. at the ratios' 1 : 2, 2 : 3), the original band of KOCN at the wavelength 2170 cm^-1 appears. Analogical measurements performed with the solutions Cu(N0₃)₂ . 3H₂0, CuCl₂. . 2H₂0, CuS0₄ . 5H₂0 and CuBr₂ and further the substitution of KOCN by NaOCN showed that the exchange of the anion does not bring about the change of the absorption of the complex; the numerical value of the absorbance (for 300 nm in the given concentration range) was equal, irrespective of the kind of cupric salt used. Following the  time changes occuring in the solutions where Cu²⁺ : OCN^- = 1 : 1.5, it was found that the character of the curve as well as the value of the absorbance change. The velocity of the changes (in 10^-3 м solutions) does not depend on the anion of the Cu(II)-salt. Graphical analysis of the dependence of the absorbance on the composition of isomolar solutions Cu(Cl0₄)₂—KOCN—methanol shows that a stable complex is formed, in which the ratio of Cu²⁺ : OCN^- = 1 : 1.5. The instability constant of this complex is about 8 . 10^-6, the molar absorptivity is 600 (for 300 nm). The ratio of Cu : OCN is indicative of the cyanate group acting as a bridge between two central Cu-atoms in the complex

Full paper in Portable Document Format: 2112a894.pdf (in Slovak)

Chemical Papers 21 (12) 894–900 (1967)