Cadmium(II) halide complexes of pyrazine

Pyrazine forms 1:1 complexes with cadmium(II) halides, CdX(2) . pyrazine (X = Cl, Br, I). The structures of all three members of this series have been determined by single-crystal X-ray diffraction. All of the complexes crystallize as infinite CdX(2) chains in which cadmium atoms are doubly bridged by pairs of halide atoms; pyrazine ligands complete the pseudo-octahedral coordination of the cadmium atoms and link the CdX(2) chains to form extended two-dimensional layers. While this type of coordination is fairly common for chloro and bromo derivatives, the iodo compound represents, to the best of our knowledge, the first example of an iodo derivative with this coordination. In each case the layers stack along the crystallographic a-axis to complete the structure. In the bromo and iodo complexes, which are isomorphous, the pyrazine ring planes are perpendicular to the plane of the layer. The chloro derivative has a very similar structure, however, the pyrazine rings are rotated by 19.3 degrees away from perpendicular, bringing the ortho-C-H groups into close proximity [2.89 (2) Angstrom] to a chloride atom. Copyright (C) 1996 Elsevier Science Ltd