The Multiphase Nature of the Cu(pz) and Ag(pz) (Hpz = Pyrazole) Systems: Selective Syntheses and Ab-Initio X-ray Powder Diffraction Structural Characterization of Copper(I) and Silver(I) Pyrazolates

Copper(I) and silver(I) pyrazolates, depending on the synthetic method used, appear in two distinct crystalline phases each. The crystal and molecular structures of the polymeric alpha-[Cu(pz)](n) and [Ag(pz)](n) and of the trimeric [Ag(pz)](3) complexes (Hpz = pyrazole) have been determined ab-initio using X-ray powder difrraction data from conventional laboratory equipment and refined with the Rietveld technique. Crystals of alpha-[Cu(pz)](n) are orthorhombic, space group Pbca (no. 61), with a = 6.6684(4) A Angstrom, b = 19.829(1) Angstrom, c = 6.0847(4) Angstrom, and Z = 8; [Ag(pz)](n) crystallizes in the orthorhombic space group Pbca (no. 61) with a = 6.5295(4) Angstrom, b = 20.059(2) Angstrom, c 6.4675(4) Angstrom, and Z = 8. A 1:1 mixed metal phase, [(Cu,Ag)(Pz)](n), has also been prepared which shows high crystallinity with lattice parameters intermediate between those of the pure Cu and Ag phases. [Ag(pz)](3) crystallizes in the orthorhombic space group Pbcn (no. 60) with a = 13.147(1) Angstrom, b = 10.570(1) Angstrom, c = 8.792(1) Angstrom, and Z = 4. For sake of comparison, the crystal structure of the polymeric beta-[Cu(pz)](n) phase has also been refined from X-ray powder diffraction data, using prior knowledge from a single crystal X-ray determination. Crystals of beta-[Cu(pz)](n), are orthorhombic, space group Pbcn (no. 60), with a = 9.933(2) Angstrom, b = 13.348(2) Angstrom, c 5.954(1) Angstrom, and Z = 8. All four polymeric complexes consist of infinite chains of linearly coordinated copper or silver atoms, bridged by bidentate pyrazolato anions, running parallel to the crystallographic c directions. As a result, the alpha-[Cu(pz)](n) and beta-[Cu(pz)](n) phases differ mainly in the interchain Cu...Cu contacts, which are as low as 2.972(6) Angstrom in the beta phase, and in the crystal packing of the polymeric chains. Of the two silver phases, [Ag(pz)](n) is isostructural with alpha-[Cu(pz)](n), while [Ag(pz)](3) is a trimeric complex of idealized D-3h symmetry, topologically similar to that already reported for the 3,5-diphenyl derivative.