Novel Copper(I) Halide Polymers:  Structures of Cu₂Br₂(2,3-dimethylquinoxaline) and (2,3-Di(bromomethyl)quinoxalinium)CuBr₂. The Continuing Saga of Copper(II) Bromide Reactivity with Organoamines

Abstract

The reaction of 2,3-dimethylquinoxaline (dmq) with copper(II) halides in water/ethanol solution yields a variety of copper(I) compounds. The major products have the stoichiometry (dmq)Cu2X2. Crystal structure analysis of the bromide compound reveals the presence of Cu4Br4 tetramers with a chair conformation. These are linked into chains by pairs of dmq ligands. Upon prolonged heating of the system, a compound can be isolated in which both of the methyl groups of the dmq molecule have been monobrominated. The crystal structure of this compound, (dBrdmqH)CuBr2, contains one dimensional (CuBr2)nn- chains of edge shared tetrahedra.