Some copper(II) and nickel(II) amine-cyanide derivatives. I. Solution equilibria

Abstract

Addition of cyanide to aqueous solutions of some copper(II) and nickel(II) tetramine complexes causes an immediate colour change, from mauve to blue for the copper compounds and orange to pink for the nickel compounds, these colours then slowly fading to colourless [Cu(CN)₄]^3- and pale yellow [Ni(CN)₄]^2- respectively as the amine complexes decompose. Spectrophotometric studies on the solutions indicate that the immediate colour change is caused by the formation of a monocyanide adduct, the formation constant being of the order of 10² for the copper(II) compounds and 10 for the nickel(II) compound studied. Measurements of the absorption spectrum and magnetic susceptibility show that the nickel(II) cyanide adduct has a triplet ground state.