Structure cristalline du complexe moléculaire HfT₄–DMF (tropolonate de hafnium–N,N-diméthylformamide)

Abstract

(Re¢u le 15juin 1976(Re¢u le 15juin , aeceptd le 8juillet 1976 The crystal structure of the molecular complex HfT4-DMF (DMF is N,N-dimethylformamide, T is the bidentate CvH~O5 tropolonato ion) has been determined by single-crystal X-ray diffraction analysis. The crystal is triclinic, space group P1, with a = 12.839, b = 10.706, c = 11.708 A, a = 67-32, fl = 101.1, ), = 83.6 °, Z = 2. The structure was solved by the heavy-atom method. 5046 reflexions with F > 3o(F) were retained for the structure determination. An anisotropic least-squares refinement was carried out to an R of 6%. The Hf atom is surrounded by the eight binding O atoms of the four tropolone ligands. The coordination polyhedron is a slightly distorted dodecahedron (42m). The geometrical parameters of the dodecahedron agree with theoretical values predicted by the 'hard-sphere' and the 'most favourable polyhedra' models. The ligand rings are planar and retain the aromatic character observed in pure tropolone. The DMF molecule is found to be planar and equidistant from two tropolone rings which belong to two different HfT 4 molecules. This configuration suggests the existence of an electrostatic interaction as a result of the high dipole moments of the DMF molecule and the tropolone rings.

Cerium Tetrakis(tropolonate) and Cerium Tetrakis(acetylacetonate) Are Not Diamagnetic but Temperature-Independent Paramagnets

“…Several crystal structures of neutral and anionic eight-coordinate metal tropolonate compounds are known, and their geometries generally are closer to that of a dodecahedron ( D 2 d ) than to that of a bicapped trigonal prism when the shape parameters are used to make this distinction. The geometries of the lanthanide anions [M­(trop) 4 ] − from Tb to Lu are close to dodecahedral, as are the neutral M­(trop) 4 , M = Zr, Hf. − The anion [Sc­(trop) 4 ] − and cation [Nb­(trop) 4 ] + are described as bicapped trigonal prisms distorted toward a dodecahedron. , …”

Synthesis and Structural Properties of Lanthanide Complexes Formed with Tropolonate Ligands

“…Since seven crystal structures of the tropolonate complexes formed with different lanthanide cations were obtained, which has been rarely reported in the literature, we were able to collect a large amount of structural information on these complexes and to perform a systematic and comparative analysis of the coordination geometry around the lanthanide cations. In order to compare the tropolonate lanthanide complexes presented here with tropolonate complexes formed with other metal ions having a coordination number of 8, the Cambridge Structure Database (CSD) was searched and six structures were identified with the coordination motif [M(Trop) 4 ] (M = Zr 4+ , Nb 5+ , Hf 4+ , Sn 4+ , Sc 3+ ). − …”

Hyperfine quadrupole coupling and .pi. bonding in dodecahedral chelates of hafnium(IV)

“…Crystals of Hf-(T)4-DMF could be produced by this method, and the structure of this molecular complex has been solved. 21 Hf(8-quin)4. According to the procedure reported by Vinogradov and Shpinel,22 tetrakis(8-hydroxyquinolinato)hafnium(IV) [Hf(8quin)4] was obtained by mixing oxalic acid and 8-hydroxyquinoline with a solution of hafnium oxychloride in 10% HC1.…”