Preparation, Spectral and Thermal Properties of Two Tetracyanopalladates(II) of Nickel(II) and the Crystal Structure of [Ni(en)3][Pd(CN)4] ] H2O

From the aqueous system Ni2+-en-[Pd(CN)4]2− (en is 1,2-diaminoethane) the complexes [Ni(en)3][Pd(CN)4] ·H2O and Ni(en)2Pd(CN)4 · 2H2O were prepared and characterized. The structure of the first one was solved using single crystal X-ray analysis; it is ionic and is formed of [Ni(en)3]2+cations, [Pd(CN)4]2− anions, and water molecules of crystallization. The hydrogen bonds of the O—H· · ·N, N—H· · ·O, and N—H· · ·N type contribute to the stabilization of the structure. The thermal decomposition reactions of both compounds were studied in the air atmosphere under dynamic conditions. The decompositions of both compounds begin with dehydration and are followed by stepwise formation of intermediate(s) with lower en contents. In the case of the second complex a phase transition concerning Ni(en)2Pd(CN)4 is observed at 140°C. The final products are oxides PdO and NiO.