POLYNUCLEAR PYRAZOLATE COMPLEXES OF COPPER - CRYSTAL AND MOLECULAR-STRUCTURES OF [CU(TMPZ)]3, [CU(3-CO2DMPZ)(TMPZH)]2CU, AND [CU(4-BR-3-CO2MEPZ)(4-BR-DMPZH)2]2 (WHERE MEPZ = METHYLPYRAZOLATE, DMPZ = DIMETHYLPYRAZOLATE, AND TMPZ = TRIMETHYLPYRAZOLATE) AND MAGNETIC-SUSCEPTIBILITY STUDIES ON THE DINUCLEAR COMPLEX

The reaction of molten trimethylpyrazole (tmpzH) with copper metal shot in air yields a mixture of the trinuclear copper(I) complex [Cu(tmpz)]3, 1, and the trinuclear copper(I/II) complex [Cu(3-CO2dmpz)(tmpzH)]2Cu, 2 (where dmpz is dimethylpyrazolate). Crystals of 1 are monoclinic, a = 8.403(3), b = 22.453(2), c = 11.362(2) angstrom, beta = 95.83(2)-degrees, Z = 4, space group P2(1)/c. Crystals of 2 are triclinic, a = 10.988(3), b = 11.009(2), c = 6.457(1) angstrom, alpha = 103.13(2)-degrees, beta = 103.02(2)-degrees, gamma = 108.70(2)-degrees, Z = 1, space group P1BAR. The reaction of molten 4-bromodimethylpyrazole (4-BrdmpzH) with copper metal shot in air gave the binuclear copper(II) complex [Cu(4-Br-3-CO2mepz)(4-BrdmpzH)2]2, 3 (where mepz is methylpyrazolate). There are two crystalline forms of 3: 3a, triclinic, a = 10.152(3), b = 13.068(3), c = 10. 033(3) angstrom, alpha = 112.38(2)-degrees, beta = 116.46(2)-degrees, gamma = 70.29(2)-degrees, Z = 1, space group P1BAR; and 3b, monoclinic, a = 13.470(1), b = 16.005(2), c = 20.174(1) angstrom, beta = 98.142(6)-degrees, Z = 4, space group C2/c. Magnetic susceptibility studies on a bulk sample of 3 (2.0-300 K) revealed antiferromagnetic coupling between the double pyrazolate bridged copper centres and analysis of the data according to a Heisenberg model for coupled pairs of S = 1/2 metal ions gave -75.4 cm-1 for the value of the exchange coupling constant, J. The crystal structures of 1, 2, 3a, and 3b were solved by the Patterson method and were refined by full-matrix least-squares procedures to final R values of 0.036, 0.056, 0.042, and 0.042 for 2265, 1764, 2011, and 2575 reflections with I greater-than-or-equal-to 3sigma(I), respectively.