Comparison of the structural parameters in copper(II) acetate-type dimers containing distorted square pyramidal CuO4O and CuO4N chromophores

A survey of 123 of copper(II) acetate-type dimeric complex units, determined by X-ray diffraction in the crystal structures containing either a CuO4O or CuO4N chromophore, gave the following results. All the distorted square pyramidal coordination spheres contain a copper atom displaced 0.165-0.225 and 0.184-0.322 Angstrom from the basal O-4 plane in CuO4O and CuO4N chromophores, respectively. The Cu-Cu distances were in the range of 2.575-2.702 and 2.603-2.886 Angstrom for the CuO4O and CuO4N chromophores, respectively. The apical ligand atoms show large coefficients of variation for the distortion from the perpendicular to the basal O-4 plane. There is highly significant propensity for the copper(II) atoms to move out from the basal O-4 plane upon elongation of the Cu-Cu distance. Strong negative correlations were found between the Cu-O-C and O-C-O angles. The most marked deviations for the observed parameters are caused by the bridges containing a halogenoacetate anion, leading to distorted trigonal bipyramidal geometry.