Dichlorobis(ethylenediamine)nickel(II) is the inorganic compound with the formula NiCl2(en)2, where en = ethylenediamine. The formula is deceptive: the compound is the chloride salt of the coordination complex [Ni<sub>2</sub>Cl<sub>2</sub>(en)<sub>4</sub>]2+. This blue solid is soluble in water and some polar organic solvents. It is prepared by ligand redistribution from [Ni(en)<sub>3</sub>]Cl2 and hydrated nickel chloride:[1]
2 [Ni(en)<sub>3</sub>]Cl2 + NiCl2 → 3 NiCl2(en)2
The rapid ligand redistribution is characteristic of the kinetic lability of octahedral nickel(II) complexes. In contrast with the lability of [Ni(en)<sub>3</sub>]Cl2+ is the inertness of the isostructural tris(ethylenediamine)cobalt(III) cation.