SPECTROCHEMISTRY OF SOLUTIONS .25. CYANO-COMPLEXATION OF NICKEL(II), PALLADIUM(II) AND PLATINUM(II) IN LIQUID-AMMONIA

A vibrational spectroscopic study of cyano-ligation of Ni(II), Pd(II) and Pt(II) in liquid NH3 has been performed. Only [Ni(CN)4]2- and [Ni(NH3)6]2+ are observed in the NiII-CN--NH3 system. In the PtII-CN--NH3 system [Pt(CN)4]2- trans-[Pt(NH3)2(CN)2] and [Pt(NH3)6]2+ exist in equilibrium. In contrast, the PdIII-CN--NH3 system slowly equilibrates (1-3 d) to mixtures containing [Pd(NH3)6]2+ [Pd(NH3)3(CN)]+, cis-[Pd(NH3)2(CN)2], [Pd(NH3)(CN)3] and [Pd(CN)4]2-, but not trans-[Pd(NH3)2(CN)2]. Infrared and Raman frequencies have been recorded. In all three systems ion pairs, in which the alkali-metal co-cation M interacts with square-planar [M'(CN)4]2- through one of its CN ligands, have been identified as stable species: [M+...-NC.M'(CN3]-. In liquid NH3, cyano-complexes of Pd(IV) and Pt(IV) are immediately reduced to Pd(II) and Pt(II).