Crown Ether Complexation of Cationic Lanthanide(III) Chloride Species Crystal and Molecular Structures of [DyCl2(H2O)2(12-crown-4)][ SbCl6].5THF (1), and [Er(12-crown-4)2(MeCN)][SbCl6]3 (2)

Department of Chemistry, University of Warwick, Coventry, CV 4 7 AL, UK
Department of Chemistry, University of Reading, Whiteknights, Reading, RG6 2AD, UK
Manuscript received 20 June 1997, accepted 3 October 1997

        Halide abstraction from a lanthanide(III) chloride using antimony(v) chloride as abstractor provides cationic metal species which can be stabilized in situ by crown ether complexation. The syntheses and structures of two such antimon(v)ate salts are presented. For [DyCl₂(12-crown-4)(H₂O)₂][SbCI₆].5THF (1) the structure comprises independent [DyCl₂(12-crown-4)(H₂O)₂]⁺ cations and SbCl6^- anions with lattice solvent (tetrahydrofuran) molecules. The cation structure has an approximate two-fold axis and the eight-coordinate metal environment can be considered as distorted square-antiprismatic. The Dy O(crown) bond distances are equivalent 2.515(11) \(\mathring{A}\) , the Dy-CI bond distances arc 2.631(5), 2.646(4) \(\mathring{A}\) and the Dy-O(H₂O) bond distances are 2.364(10), 2.373(11) \(\mathring{A}\) . In the case of [Er(12-crown-4)₂(MeCN)][SbCl₆]₃ (2) the independent nine-coordinate [Er(12-crown-4)₂(MeCN)]³⁺ cations show crystallographic C₂ symmetry with each metal centre being bonded to all four oxygen atoms of the two rings and to a nitrogen atom of a coordinated acetonitrile molecule. The Er-O(crown) bond lengths lie in the range 2.443(9)-2.503(9) \(\mathring{A}\) , mean 2.463(9) \(\mathring{A}\)  and the Er-N bond length is 2.56(2) \(\mathring{A}\) . The planes of the two oxa-crown rings intersect at an angle of 73.0(1)°