Crystal Structures of the Complexes of Zn(II), Cd(II), and Hg(II) with 1,2,5-Selenadiazolopyridine: Ligation of N vs Se ?

The coordination ability of 1, 2, 5-selenadiazolopyridine (psd) towards MCl2 (M = Zn, Cd, Hg), and HgBr2 has been investigated. The 2:1 reactions of psd with MCl2 and HgBr2 afforded dimeric [(psd)(2)ZnCl2](2), polymeric [(psd)(2)CdCl2] n and monomeric (psd)(2)HgBr2 complexes. The 1:1 reactions of psd with HgX2 (X = Cl, Br), gave only polymeric complexes i.e. [(psd) HgX2](n). Single crystal X-ray diffraction studies of the complexes reveal that psd ligand coordinates to the metal ions either through azole N or pyridine N. In no case, coordination through the selenium donor was observed. These observations are also supported by DFT calculations. Complex [(psd)(2)CdCl2](n) is a 3D supramolecular framework extended by Cl -> Cd dative bond, Se center dot center dot center dot N-py secondary bonding and C-H center dot center dot center dot Cl hydrogen bonding interactions