Crystal structure of the basic erbium tetramethyl-heptanedionate, Er8O(thd)10(OH)12

Abstract

The crystal structure of the basic erbium diketonate, Er8O(thd)10(OH)12, which occurs as a minor by-product in the synthesis of tris(2,2,6,6-tetramethylheptane-2, 5-dionato)erbium(III), Er(thd)3, has been studied at room temperature by X-ray diffraction. The space group isPbcn and the crystal data area = 18·376(19),b = 31·625(35),c = 27·914(28) A,Z = 4,D c = 1·38 gcm−3,D m = 1·37 gcm−3. Full-matrix least-squares refinement of atomic and isotropic thermal parameters, using 3103 non-zero intensities obtained by counter methods, terminated with a conventionalR of 0·116. The Er atoms were found to be chelated by one thd group each and to cluster around a central oxygen atom. An inner sphere of four erbium atoms which surround the oxygen in a distorted tetrahedral fashion are bonded to five hydroxyl groups each and are eight-coordinate. An outer sphere of four erbiums which formally complete a dodecahedron around the central oxygen are bonded to four hydroxyl groups each and are seven-coordinate. The seventh ligand atom belongs to a non-chelating thd group which is bonded through oxygen to two different erbium atoms. Each hydroxyl group is bonded to three erbium atoms, two of which belong to either the inner or the outer sphere. The coordination geometries of the erbium ions are all related to capped trigonal prisms and thet-butyl groups are directed outwards. As a consequence the material behaves as a typical non-polar substance and sublimes together with Er(thd)3, apparently without decomposition.