Synthesis and properties of some lanthanoid(III) perchlorates with macrocyclic polythioethers of the [18]-crown-6-type. Crystal structure of aquadiperchlorato(1,4,10,13-tetraoxa-7,16-dithiacyclo-octadecane)-lanthanum(II) perchlorate
Abstract
Some complexes of lanthanoid(III) perchlorates have been prepared with three polythia macrocycles of the [18]-crown-6 type. By using the ligand 1,4,10,13-tetraoxa-7,16-dithiacyclo-octadecane, L1, in methyl cyanide, three series of complexes have been obtained with formulae (i) Ln[ClO4]3·L 1·H2O (Ln = La, Ce, or Pr), (ii) Ln[ClO4]3·L 1·H2O·x MeCN (Ln = Ce, Pr, Nd, Sm, Eu, Ho, or Yb; x= 1.5 or 2), and (iii) Nd[ClO4]3·L1. The crystal and molecular structure of the title complex has been determined by X-ray diffractometric data. The structure has been refined by least-square techniques to R= 0.036 for 4 635 observed reflections. The lanthanum(III) ion is ten-co-ordinated to the six donor atoms of L1, to two oxygen atoms of a [ClO4]– ion, to an oxygen atom of a second [ClO4]–, and to an oxygen atom of a water molecule. The co-ordination polyhedron can be described as a decatetrahedron. The macrocycles 1,10-dioxa-4,7,13,16-tetrathiacyclo-octadecane, L2, and 1,4,7,10,13,16-hexathiacyclo-octadecane, L3, do not co-ordinate to lanthanoid(III) perchlorates in methyl cyanide but in dichloromethane the complexes Eu[ClO4]3·L 2·H2O and Ln[ClO4]3·L 3·H2O (Ln = Sm, Eu, or Yb) can be isolated. The i.r. and electronic spectra of all the complexes are discussed. The electron-transfer transitions are consistent with an optical electronegativity value of 2.8 for ligand L1 and 2.7 for L2 and L3.