Synthesis, crystal structure and magnetic properties of a (mu-hydroxo)(mu-pyrazolato) dicopper(II) complex

Preparation and magnetic properties of a 3,5-dimethylpyrazolate bridged bin uclear copper(II) complex [Cu-2(L)(3,5-pyz)] (L = 1,3-Bis(2-Hydroxy-5-Chlor osalicylideneamino)propan- 2-ol) is reported. The crystal structure determi ned by X-ray diffraction methods. (C22H20N4O3Cl2CU2), triclinic, space grou p P (1) over bar, a = 9.622(3), b = 10.921(2), c = 11.420(3) Angstrom, alph a = 100.73(2), beta = 94.04(2), gamma = 108.08(2)degrees V = 1110.2(5)Angst rom(3), Z = 2. TWO copper(II) ions in a square-planar coordination are brid ged via alkoxide oxygen and 3,5-dimethyl pyrozolate nitrogen atoms to form a dinuclear unit. The metal coordination sphere is four-coordinate, planar with an N2O2 donor set. The dihedral angle between the two coordination pla nes is 166.83 degrees. There are significant intermolecular interactions be tween neighbouring binuclear entities. The shortest intermolecular Cu(1)... Cu(1)(i) distance is 3.383(1) Angstrom and the Cu(1) - O(1)(i) distance is 2.666(3) Angstrom (i = 1-x, -y, 1-z). The variable-temperature magnetic su sceptibility measurement for a powdered sample of the complex was carried o ut in the temperature range 5 - 350 K and analysed to obtain values of the parameter J in the exchange Hamiltonian H = -2JS(Cu). S-Cu; 2J = -164 cm(-1 ). The magnetic moment at 300 K is about 2.42 mu(B), and 0.22 mu(B) at 5 K. The weak antiferromagnetism of the present complex is reasonably explained in terms of the orbital countercomplementary effect based on Hoffmann's th eory for super-exchange interaction.