Three new complexes [M(deten)2Ni(μ-CN)2(CN)2] n (M = Ni, Cu and Cd, deten = N,N-diethylethylenediamine) have been synthesized and characterized by chemical, thermal analysis, FT-IR and Raman spectroscopies. The crystal structure of the Cd complex has been determined by X-ray single crystal diffraction. Structural study reveals that the Ni2+ and Cd2+ ions are located on inversion centers, and adopt slightly distorted square-planar and octahedral geometries, respectively. In the crystal structure, the intermolecular N–H⋯N hydrogen bonds link the polymeric chains into a two dimensional network. Vibrational spectral data indicate the presence of two ν(C≡N) for complexes can be assigned to the terminal and bridging cyanides. The decomposition reaction take places in the temperature range 30–1000 °C in the static air atmosphere.