DIFFERENT PICRATE COORDINATION MODES ALONG THE LANTHANIDE SERIES - SYNTHESIS AND MOLECULAR-STRUCTURE OF 2 ISOMORPHOUS COMPOUNDS [LN(2)(PIC)(4)(TDTD)(3)(H2O)(2)] (PIC)(2)(H2O)(2) (LN = TM, LU PIC = PICRATE TDTD= TRANS-1,4-DITHIANE-S,S'-DIOXIDE)

The two isomorphous compounds [Ln(2)(pic)(4)(TDTD)(3)(H2O)(2)] (pic)(2 )(H2O), (Ln = Tm, Lu; pic = picrate; TDTD = trans-1,4-dithiane-S,S'-di oxide) were synthesized and characterized by IR spectra and X-ray sing le-crystal structure analysis. The two independent metal cations have subtly different coordination spheres. One is eight coordinated with a square antiprismatic coordination geometry resulting from the bonding of two chelating picrate ligands, three oxygens of the TDTD ligands a nd water molecules. For the other the eighth Ln-O(NO) contact is consi derably longer, giving a seven coordinate endcapped trigonal prism. Th e sharing of the TDTD moieties among adjacent units results in the for mation of polymeric structures in which uncoordinated picrate anions a nd water molecules are clathrated. (C) 1998 Elsevier Science S.A. All rights reserved.