UNUSUAL BEHAVIOR OF ISOCYANATE AND HALIDE COMPLEXES OF COPPER(2)

Tetracyanato and tetrahalo complexes of copper(II) show interesting and heretofore unobserved properties in both the solid state and in various non-aqueous media. Various salts of the isocyanato and halocuprate(II) anion involving tetraethylammonium and other bulky cations were prepared. In the cases of tetraphenylphosphonium and tetraphenylarsonium salts of the tetraisocyanatocuprate(II) anion, geometric isomers (blue and yellow) were isolated from alcohol-water solutions of cupric nitrate, potassium cyanate, and tetraphenylphosphonium chloride or tetraphenylarsonium chloride upon evaporation at room temperature. All the tetraisocyanatocuprate(II) salts yielded greenish-yellow solutions when dissolved at room temperature in chloroform, dichloromethane, nitromethane, or acetone which became bright yellow when warmed and generally developed a blue color when cooled to dry ice temperature. Absorption spectra of these solutions from 320 to 1000 mμ were studied from -55°C to +45°C, and reflectance and infrared absorption spectra of the various solid compounds were recorded. Magnetic moments, obtained by the Gouy method, revealed that the blue and yellow forms of the tetraphenylphosphonium and tetraphenylarsonium tetraisocyanatocuprate(II) salts were distinctly different species of identical composition. It is proposed that the four NCO entities are arrayed about the copper in a square planar (or pseudo octahedral) manner in the blue isomer and in a tetrahedral (though probably distorted) fashion in the yellow form. © 1969.