Reversible nitro-nitrito inter-conversion in a simple mono-nuclear nickel(II) complex [NiII{C6H4(NH2)2}2(NO2)2] in the solid state

A simple mono-nuclear nickel(II) complex [Ni-II{C6H4(NH2)(2)}(2)(NO2)(2)] (1) has been synthesized from an aqueous solution containing nickel chloride, sodium nitrite and ortho-phenylenediamine (opda). When crystals of compound I are heated in the temperature range of 110-120 degrees C for 5 min, their brown color changes to blue, that is accompanied by the conversion of nitro group (N-coordinated) in compound 1 into nitrito group (N-coordinated) in compound [Ni-II{C6H4(NH2)(2)}(2)(ONO)(2)] (2). On cooling, the nitrito compound 2 goes back to parent nitro-compound 1. (c) 2009 Elsevier B.V. All rights reserved.