Synthesis and characterization of three 5-(4-pyridyl)tetrazolato complexes obtained by reaction of 4-cyanopyridine with metal azides from aqueous solutions

Abstract

Three metal complexes with the 5-(4-pyridyl)tetrazolate anion, (4-PTZ) −, as ligand were obtained by the reaction of 4-cyanopyridine with corresponding metal azides in aqueous solution. Isomorphic complexes of composition [M(4-PTZ) 2(H 2O) 4] · 2H 2O with M=Mn(II) ( 1) and Cd(II) ( 2) were obtained, whereas [Ca 1.5((4-PTZ) 2H)(N 3) 2(H 2O) 5](H 2O) 0.3 ( 3) was separated from calcium azide solutions. The IR spectra and the thermal behaviour of the complexes are measured and discussed. The single crystal X-ray diffraction revealed that the isomorphous structures of 1 and 2 consist of octahedrally coordinated metal centers, where two 4-PTZ anions act as monodentate ligands via their pyridine-N atoms in trans-positions. The structures also contain six water molecules, four act as monodentate ligands and the remaining two as lattice water molecules. Hydrogen bonds of the types O–H…O and O–H…N connect the mononuclear units to a three-dimensional network structure. The chain structure of complex 3 features octahedrally coordinated Ca(1); dinuclear subunits of pentagonal-bipyramidal Ca(2) centers; azide groups acting in end-on and end-to-end bridging mode; a (4-PTZ) 2H ligand in its zwitter ionic form coordinated via N(1) atom of the tetrazole ring to Ca(2), as well as lattice and ligand water molecules. Again, a complicated hydrogen bond system connects the chains of polyhedra to form a 3-D network structure.