Oxidation and reduction of tetracyanonickelate(II) ions induced by ionizing radiation : an electron spin resonance study of the [Ni(CN)4]3–, [Ni(CN)4]–, and [HNi(CN)4]2– complexes

Abstract

Exposure of salts and aqueous glasses containing tetracyanonickelate(II) ions to ⁶⁰Co γ-rays at 77 K gives [Ni(CN)₄]^3–(d⁹) and [Ni(CN)₄]^–(d⁷) ions, identified by their g-tensor components, which are markedly dependent upon the medium. For the d⁹ complexes this dependence is assigned to interaction with the cyanide ligands, and for the d⁷ complexes to interactions in the axial sites. The former ions have a…d¹_x²–y² configuration, and the latter a …d¹_z² configuration on nickel. In the potassium salt, and in aqueous glasses containing methanol, d⁷ centres are formed whose e.s.r. spectra exhibit large hyperfine coupling to one ¹⁴N nucleus. In certain cases, especially for the barium salt, a novel species exhibiting large hyperfine coupling (ca. 150 G) to a single proton has been detected. This is identified as the complex [HNi(CN)₄]^2–.