• White, Allan H.
• Harrowfield, Jack M.
• Chan, Eric J.
• Skelton, Brian W.
• Sobolev, Alexandre

Abstract

<p>Crystalline products of the reactions of lanthanide picrates, Ln(pic)₃ (pic = 2,4,6-trinitrophenoxide), with hexamethylphosphoramide (hmpa) and octamethylpyrophosphoramide (ompa) have been characterised by single-crystal X-ray diffraction studies. With hmpa and lighter lanthanides (La, Sm, Eu), isomorphous species (monoclinic, P2₁/c, Z 4) of stoichiometry [Ln(pic)₃(hmpa)₃]·0.5H₂O, have been defined where the molecular units in the lattice contain 9-coordinate Ln with tricapped trigonal-prismatic coordination geometry. The picrate ligands are bidentate through phenoxide-O and 2-nitro-O, with the latter occupying the capping positions, while the hmpa ligands are singly O-bound to one trigonal face. Heavier lanthanides (Gd, Lu) and Y have been found to give isomorphous (monoclinic, P2₁/n, Z 4) species of stoichiometry [Ln(pic)₃(hmpa)₂], with 8-coordinate Ln of an irregular geometry best considered as close to that of a bicapped trigonal-prism. The picrate ligands chelate in the same manner as in the lighter Ln complexes but with one spanning a trigonal edge, and the hmpa-O donors occuping two apices of the other trigonal face. The ligand ompa has been found to act as a bidentate chelate in all isolated species, displacing one picrate from the metal ion coordination sphere to give ionic complexes. For La, Nd, and Gd, isomorphous (monoclinic, P2₁/n, Z 4) complexes of stoichiometry [Ln(pic)₂(ompa)₂(OH₂)](pic)·0.5H₂O containing 9-coordinate, tricapped trigonal-prismatic Ln with a single aqua ligand have been defined, while for Er, Yb, Lu, and Y, both the coordinated and lattice water molecules are lost in isomorphous (monoclininc, P2₁/c, Z 8) 8-coordinate, square-antiprismatic species of stoichiometry [Ln(pic)₂(ompa)₂](pic). For Er, further polymorphs, one monoclinic, P2₁/c, and the other triclinic, CH19251-IE1.gif, have also been characterised.</p>

Topics

• x-ray diffraction
• Lanthanide