Formation and reaction of trichloro complexes of bivalent transition metals in 1,2-dichloroethane

Abstract

Trichloro complexes of some bivalent transition metals (M²⁺) have been prepared in tetra-n-butylammonium chloride–1,2-dichloroethane solution saturated with the metal chlorides. Their chemical forms and reactions, and the effect of water, have been investigated by means of spectrophotometry and vapour-pressure osmometry at 25.0 °C. Copper(II) and cadmium(II) form monomeric tetrahedral trichloro complexes containing one water molecule, NBu₄[MCl₃(H₂O)], whilst cobalt(II) forms a dimeric tetrahedral trichloro complex [NBu₄]₂[Co₂Cl₆]. Zinc(II) exists as a mixture of monomeric and dimeric forms. Manganese(II) and nickel(II) do not form trichloro complexes. Copper(II) forms a monomeric tetrachloro complex. Cobalt(II) forms a monomeric tetrachloro complex and a trichloromono(pyridine base) complex by reaction with NBu₄Cl and with pyridine base, respectively. The formation constants of the copper(II) and cobalt(II) complexes have been evaluated by means of spectrophotometry. The effect of water on the equilibria of the trichloro complexes of copper(II) and cobalt(II) is discussed.