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 MCl 2 (M = Zn, Cd, Hg), and HgBr 2 has been investigated. The 2:1 reactions of psd with MCl 2 and HgBr 2 afforded dimeric [(psd) 2 ZnCl 2 ] 2 , polymeric [(psd) 2 CdCl 2 ] n and monomeric (psd) 2 HgBr 2 complexes. The 1:1 reactions of psd with HgX 2 (X = Cl, Br), gave only polymeric complexes i.e. [(psd)HgX 2 ] 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 CdCl 2 ] n is a 3D supramolecular framework extended by Cl→Cd dative bond, Se···N py secondary bonding and C–H···Cl hydrogen bonding interactions.