title: The monolanthanide-containing silicotungstates [Ln(beta2-SiW11O39)2]13- (Ln = La, Ce, Sm, Eu, Gd, Tb, Yb, Lu): a synthetic and structural investigation.
abstract: We have synthesized and structurally characterized the monolanthanide-containing polyanions [Ln(beta2-SiW11O39)2]13- (Ln = La (1), Ce (2), Sm (3), Eu (4), Gd (5), Tb (6), Yb (7), Lu (8)). Synthesis was accomplished by reaction of the respective lanthanide ion with the monolacunary Keggin-type precursor [beta2-SiW11O39]8- in a 1:2 molar ratio in 1 M KCl medium at pH 5. Polyanions 1-8 were isolated as potassium salts and then characterized by IR, single-crystal X-ray diffraction, and elemental as well as thermogravimetric analysis. The structures of 1-8 are composed of an eight-coordinated Ln3+ center sandwiched by two chiral (beta2-SiW11O39) units. Large Ln3+ ions appear to favor an (R,R) (or (S,S)) configuration (point group C2) of the Keggin units, with an increasing amount of (R,S) (or (S,R)) configuration (point group C1) found in the solid state as the Ln3+ ion decreases in size. This trend is also supported by solution 183W NMR results for the diamagnetic La3+ and Lu3+ derivatives.
authors.affiliation: School of Engineering and Science, International University Bremen, P.O. Box 750 561, 28725 Bremen, Germany.
authors.forename: Bassem S
authors.initials: BS
authors.lastname: Bassil
authors.forename: Michael H
authors.initials: MH
authors.lastname: Dickman
authors.forename: Bernd
authors.initials: B
authors.lastname: von der Kammer
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kortz
mesh_terms: D007536:Isomerism; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D012825:Silicon / Q000737:chemistry*; D017973:Tungsten Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D028581:Lanthanoid Series Elements; D017973:Tungsten Compounds; C045951:tungstate; D012825:Silicon