MAGNETIC-PROPERTIES AND CRYSTAL-STRUCTURE OF (MU-PYRAZINE)-BIS[(AQUA)(2,6-XYLYLAMINODIACETATO)COPPER(II)] - A PYRAZINE-BRIDGED DINUCLEAR COPPER(II) COMPLEX

The preparation, spectroscopic and magnetic study, and crystal structure of the complex {mu-pyrazine}bis[(aqua)(2,6-xylylaminodiacetato)copper(II)], [Cu2(L)2(H2O)2(pyz)], are reported. It crystallizes in the monoclinic space group P2(1)/n with cell constants a = 13.309(3), b = 7.590(2), c = 15.459(3) angstrom, beta = 100.90(3)-degrees, Z = 2, R = 0.038, R(w) = 0.045. The structure consists of neutral dinuclear [Cu2(L)2(H2O)2(pyz)] Molecules, in which the copper(II) ions are bridged by a molecule of pyrazine, with a Cu ... Cu distance of 5.786 angstrom. Each of the CuN2O3 coordination polyhedra can be described as a square-based pyramid with a small distortion toward trigonal-bipyramid. The bridging pyrazine molecule is bonded in equatorial position and canted out of the basal coordination plane by 20.8-degrees. The magnetic study indicates that a weak antiferromagnetic interaction operates between the copper(II) ions with an exchange coupling constant of -3.7 cm-1. The magnitude of the exchange interaction is discussed on the basis of structural data.