CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF BIS(PYRAZINE)COPPER(II) PERCHLORATE, CU(PYZ)2(CLO4)2, A 2-DIMENSIONAL HEISENBERG ANTI-FERROMAGNET

The crystal and molecular structure of Cu (pyz)2(C1O4)2, where pyz is pyrazine, has been determined by using heavy-atom, least-squares, X-ray methods for 1027 reflections measured on a computer-automated four-circle diffractometer. The complex crystallizes in the space group C2/min a unit cell with a=14.123 (4) υ, b=9.781 (2) υ, c=8.984 (2) υ,β=147.12 (2)°, Pobsd=2.08 (1) g/cm3, and=2.09 g/cm3. The structure was refined to final discrepancy indices of R=0.052 and Rw=0.069. The complex consists of sheets of copper (II) ions bridged by ambidentate pyrazine ligands. The distance between two adjacent sheets is 7.012 υ. The dihedral angle between the plane of each pyrazine ligand and the sheet in which it is located is 66.1°. The coordination geometry about each copper(II) ion is that of a tetragonally elongated octahedron, where each copper (II) ion is bonded strongly [Cu-N=2.062 (3) υ] to four pyrazine ligands and weakly [Cu-O=2.373 (12) υ] to two perchlorate ions. The magnetic susceptibility vs. temperature data (4.2-285 K) were least-squares fit to a theoretical equation for a two-dimensional Heisenberg antiferromagnet. © 1979, American Chemical Society. All rights reserved.