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 α-[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 β-[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 cm3 K mol−1, θ = 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.
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Stassen et al. (2003) studied this question.