Linkage isomers of dibromobis(1-(2-methoxyethyl)tetrazole)copper(II) containing either a bromide or a unique tetrazole bridge

The ligand 1-(2-methoxyethyl)tetrazole (teeOMe) reacts with copper(II) bromide to form two different isomers with the formula [Cu (teeOMe)2Br2]n. The coordination details on the crystal packing are determined by the solvent from which the compound crystallises. In methanol, green crystals of (alpha)-[Cu(teeOMe)2Br2](1) are formed, and these have been characterised by X-ray crystallography (at three temperatures) and magnetic susceptibility measurements. The crystal structure of 1 is built up from square-planar trans-[Cu (teeOMe)2Br2] units. Additional weak axial interactions between the copper centers and the N(2) tetrazole atoms of neighbouring complexes link the [Cu(teeOMe)2Br2] units into two-dimensional layers. Compound 1 displays paramagnetic behaviour (C= 0.41 cm3 K mol^-1). In ethanol, yellow-brown crystals of (beta)-[Cu(teeOMe)2Br2](2) are formed, and these have been characterised by magnetic susceptibility measurements, in addition to IR, ligand field and EPR spectroscopy. The observed magnetic behaviour (C= 0.41 cm^3 K mol^-1, (theta)= 30.5 K and J/kB= 16.4 K) is consistent with a structure containing two-dimensional bromide-bridged copper(II) grids. It is proposed that in 2 the square-planar [Cu(teeOMe)2Br2] units are connected via axial Cu-Br interactions, as deduced from comparison of the magnetic properties.