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.