The direct reaction of lanthanoid metals with 3,5-diphenylpyrazole (Ph2pzH) at 300 °C under vacuum in the presence of mercury gives the structurally characterized [Ln3(Ph2pz)9] (Ln = La or Nd), [Ln2(Ph2pz)6] (Ln = Er or Lu). Similar reactions provided heteroleptic [Ln(Ph2pz)3(Ph2pzH)2] (Ln = La, Nd, Gd, Tb, Er and Y). The last was obtained only from impure Ph2pzH, but was subsequently prepared by treatment of [Yb(Ph2pz)3(thf)2] with Ph2pzH. Reactions of Yb with Ph2pzH at 200 °C gave a poorly soluble divalent species which was converted by 1,2-dimethoxyethane into [Yb(Ph2pz)2(dme)2]. Single crystal X-ray structures established a bowed trinuclear pyrazolate-bridged structure for [Ln3(Ph2pz)9] (Ln = La or Nd), LnLnLn being 135.94(1)° (La) and 137.41(1)° (Nd). There are two η2-Ph2pz ligands on the terminal Ln atoms and one on the central metal with adjacent Ln atoms linked by one μ-η2:η2 and one μ-η5 (to terminal Ln):η2 pyrazolate group. Thus the terminal Ln atoms are formally nine-coordinate and the central Ln, ten-coordinate. By contrast, [Ln2(Ph2pz)6] (Ln = Er or Lu) complexes are dimeric with two terminal (η2) and two bridging (μ-η2:η2) pyrazolates and eight-coordinate lanthanoids. All six heteroleptic complexes [Ln(Ph2pz)3(Ph2pzH)2] (Ln = La, Nd, Gd, Tb, Er or Yb) are isomorphous with three equatorial η2-Ph2pz groups, transoid (N–Ln–N 158.18(6)–161.43(9)°) η1-pyrazole ligands, and eight-coordinate Ln throughout.
|Publication status||Published - 2004|