Crystal and molecular structure of dichlorotris-(1,2-dimethylimidazole)copper(II); a trigonal-bipyramidal complex showing elongation of the equatorial Cu–N bond

Abstract

The structure of dichlorotris-(1,2-dimethylimidazole)copper(II), CuCl₂(C₅H₈N₂)₃, has been determined by three-dimensional X-ray structure analysis and refined by least-squares methods using 3018 independent reflections to R= 0·032. The crystals are orthorhombic, with unit-cell dimensions a= 15·205, b= 8·791, c= 29·81 Å, space group Pca2₁, and Z= 8. The complex is monomeric, and there are no chemically significant differences between the two crystallographically independent molecules in the cell. The copper atom has a trigonal-bipyramidal co-ordination, with the equatorial positions occupied by two chlorine atoms and a donor nitrogen atom. The equatorial Cu–N bonds (2·145 Å) are appreciably longer than the axial ones (2·005 Å). This is discussed in terms of the stereochemical influence of the half-filled d_z² orbital in this type of co-ordination. In all molecules the two Cu–Cl bonds are slightly different, with average lengths of 2·370 and 2·414 Å.