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

Abstract

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/k_B = 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.