A new type of copper complex as found in the crystal structure of cupric acetate, Cu 2 (CH 3 COO) 4 .2H 2 O

Abstract

Crystals of cupric acetate are monoclinic with space group C2/c. The unit cell, of dimensions a----13.15, b = 8.52, c----13.90 A, fl----117 ° 0', contains four Cu2(CHaCOO)4.2 HeO molecules. The symmetry centre of this binuclear molecule coincides with a symmetry centre of the C2/c space group. Projections of the structure on three crystallographic planes are given. The four acetate groups in a single molecule are separately planar and have normal bond distances and angles. The way in which they bridge the two copper atoms in a molecule is illustrated. The most striking feature of this sixfold co-ordinated copper complex is the close approach of 2.64 A between the two copper atoms. In this unusual configuration each of the two copper atoms forms, in addition to four co-planar bonds to four oxygen atoms, also a bond to a copper atom and to a water molecule. The nature of these bonds is open to speculation. Hydrogen bonds appear to be mainly responsible for the forces between molecules. The way in which the molecules are packed in the structure is illustrated.