Synthesis, structure, network and thermal analysis of four 5-(pyrazinyl)tetrazolato copper(II) and cobalt(II) complexes

Abstract

Three new copper complexes and one cobalt complex with 5-(pyrazinyl)tetrazolate anion, (pyztz) −, as chelating bidentate ligand, were obtained by the reaction of pyrazinecarbonitrile with sodium azide in the presence of copper(II) nitrate or cobalt(II)chloride. Complexes of composition [Cu(pyztz) 2(H 2O)] ( 1) deep blue crystals, [Cu(pyztz) 2(H 2O) 2] ( 2a) green crystals, [Co(pyztz) 2(H 2O) 2] ( 2b) orange crystals, [Cu(pyztz) 2(H 2O) 2] · (H 2O) ( 3) blue crystals were obtained. The single crystal X-ray diffraction revealed that complex 1 has square pyramidal structure with one water molecule at apical and two pyrazine-tetrazolato ligands at basal sites, while structures of 2a, 2b and 3 consist of octahedrally coordinated metal ions, where two pyztz anions act as bidentate ligands via one of the pyrazine-N atoms and one of the tetrazole-N atoms in trans-positions and two trans water molecules. Complex 3 contains one extra lattice water molecule. Hydrogen bonds of the types O–H⋯O and O–H⋯N connect the mononuclear units to a three-dimensional network structure in 2 ( a and b are isostructural) and 3. Although the H-bond patterns look complex it is shown that they can be related to the well-known three- and six-connected rutile net ( rtl) in 2 and the four- and six-connected fsh-net in 3.