CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF TETRAKIS(CYCLOHEXYLAMINE)DI-MU-HYDROXO-DICOPPER(II) PERCHLORATE - 1ST EXAMPLE OF A ROOF-SHAPED HYDROXO-BRIDGED COPPER(II) DIMER

The title compound [Cu(C6HnNH2)2OH]2(ClO4)2 was synthesized and its crystal structure solved at room temperature from 6429 independent reflections. It crystallizes in the monoclinic system, space group C2/c. The lattice constants are a = 27.77 (1) Å,b= 14.45 (1) Å, c = 17.68 (1) Å, and β = 91.7 (1)° with Z = 8. Least-squares refinement of the structure led to a conventional weighted R factor of 0.069 excluding zeros. High thermal vibrations of perchlorate groups and cyclohexyl rings limited the refinement. The structure is made of roof-shaped binuclear units [Cu(C6H11NH2)20H]22+ with a dihedral angle of 147.5° and of essentially noncoordinated perchlorate anions. The temperature dependence of the magnetic susceptibility, studied in the range 10-300 K, shows an intramolecular antiferromagnetic coupling with a singlet-triplet separation of -256 cm-1. According to Hatfield and Hodgson's correlation, the planar hydroxo-bridged Cu(II) dimer derived from the title compound by opening the dihedral angle up to 180° should exhibit a singlet-triplet separation of about -600 cm-1. The influence of the bending on the magnetic properties was studied in the framework of a previously described orbital model. © 1979, American Chemical Society. All rights reserved.