SYNTHESES, STRUCTURES, AND REACTIVITY OF POLYNUCLEAR PYRAZOLATO COPPER(I) COMPLEXES, INCLUDING AN AB-INITIO XRPD STUDY OF [CU(DMNPZ)](3) (HDMNPZ = 3,5-DIMETHYL-4-NITROPYRAZOLE)

The reaction of [Cu(CH3CN)(4)](BF4) with 3,5-dimethyl-4-nitropyrazole (Hdmnpz) in the presence of triethylamine yields the new copper(I) com plexes [Cu(dmnpz)](3) (1) and (Et3NH)(2)[Cu-4(dmnpz)(6)] (2), dependin g on the experimental conditions. The reactivity of 1 and 2 toward neu tral ligands such as triphenylphosphine, cyclohexyl isocyanide (RNC), and carbon monoxide has been investigated. In particular, both complex es readily react with RNC, giving the dinuclear complexes [Cu(dmnpz)(R NC)](2) (4) and [Cu(dmnpz)(RNC)(2)](2) (5), depending on the copper/RN C ratio, and with PPh3, affording the dimeric derivative [Cu(dmnpz)(PP h3)](2) (6). The crystal and molecular structure of 1 has been determi ned ab initio using X-ray powder diffraction data from conventional la boratory equipment. Crystals of 1 are monoclinic, C2/c, a = 20.057(2) Angstrom, b = 13.816(2) Angstrom, c = 7.883(1) Angstrom, beta = 95.912 (4)degrees; R-F and R-wp 0.067 and 0.039, respectively, for Rietveld r efinement on 3900 data points collected in the range 17 < 2 theta < 95 degrees (Cu K alpha radiation). Crystals of 1 contain planar trimers, with the copper atoms bridged by exo-bidentate ligands and short inte rmolecular Cu ... Cu contacts (3.329(7) Angstrom). For complexes 2 and 4-6, single-crystal X-ray diffraction studies have been performed. Cr ystals of 2 are monoclinic, P2(1)/c, a = 11.026(1) Angstrom, b = 13.45 6(2) Angstrom, c = 18.668(5) Angstrom, beta = 92.91(2)degrees, Z = 2. The ionic packing of 2 contains tetranuclear complexes, with the coppe r atoms connected by six dmnpz ligands. Crystals of 4 are triclinic, P (1) over bar, a = 7.418(1) Angstrom, b = 9.780(1) Angstrom, c = 11.17 7(3) Angstrom, alpha = 109.61(2); beta = 101.34(3)degrees, gamma = 105 .82(1)degrees, Z = 2. Crystals of 5 are triclinic, P (1) over bar, a = 9.506(4) Angstrom, b = 9.957(2) Angstrom, c = 11.658(4) Angstrom, alp ha = 86.73(2)degrees, beta = 79.54(2)degrees, gamma = 82.47(4)degrees, Z = 1. Crystals of 6 are triclinic, P (1) over bar, a = 11.379(2) Ang strom, b = 13.592(2) Angstrom, c = 14.409(3) Angstrom, alpha = 81.22(1 )degrees, beta = 85.21(1)degrees, gamma = 87.55(1)degrees, Z = 2. 4, 5 , and 6 are binuclear complexes bearing one RNC, two RNC, and one trip henylphosphine ligands on each copper atom, respectively. The steric r equirement of the dmnpz ligands, in the presence of RNC or PPh3, force s the inner [Cu-2(dmnpz)(2)] core of the three complexes into markedly different conformations.