Four [Cd(L)2(N3)2]n 1D systems with different azide bridging sequences: Synthesis, spectral and structural characterization

Four new cadmium(II) complexes: [Cd(4-Etpy)2(N3)2]n (1) (4-Etpy = 4-ethylpyridine), [Cd(3-acpy)2(N3)2]n (2) (3-acpy = 3-acetylpyridine), [Cd(4-OHMepy)2(N3)2]n (3), (4-OHMepy = 4-hydroxymethylpyridine) and [Cd(3-OHMepy)2(N3)2]n (4), (3-OHMepy = 3-hydroxymethylpyridine), are synthesized and structurally characterized. The IR spectra of the complexes are measured and discussed. The single crystal X-ray diffraction revealed that all of these four complexes exhibit 1D [Cd2(N3)2]n chains, six-coordinate cadmium centers and trans arrangement of the two pyridines. In the structure of 1, the azide groups in the double bridges are alternately in the μ-1,3 and μ-1,1 modes between neighboring cadmium atoms, whereas in 2 the chain is formed only from double μ-1,1 azide bridges. In the structure of 3, the double azido bridges show the unprecedented –Cd-(μ-1,1-N3)2–Cd-(μ-1,1-N3)2–Cd-(μ-1,1-N3)2–Cd-(μ-1,3-N3)2–Cd– sequence. In the structure of 4, each pair of cadmium centers is simultaneously bridged by two different azides: μ-1,1 and μ-1,3 bridges. In the chain of polyhedra these μ-1,1 and μ-1,3 azido bridges are trans to each other. In all of the four complexes the μ-1,1 azides are asymmetric whereas the μ-1,3 azido ligands are more symmetric, and the azides of both types are almost linear within the experimental error.