title: A Novel Dimeric Ni-Substituted beta-Keggin Silicotungstate: Structure and Magnetic Properties of K(12)[{beta-SiNi(2)W(10)O(36)(OH)(2)(H(2)O)}(2)].20H(2)O.
abstract: The novel dimeric polyoxometalate [{beta-SiNi(2)W(10)O(36)(OH)(2)(H(2)O)}(2)](12)(-) (1) has been synthesized and characterized by IR spectroscopy, polarography, elemental analysis, thermogravimetric analysis, and magnetic measurements. An X-ray single-crystal analysis was carried out on K(12)[{beta-SiNi(2)W(10)O(36)(OH)(2)(H(2)O)}(2)].20H(2)O, which crystallizes in the monoclinic system, space group P2(1)/n, with a = 13.701(4) Å, b = 24.448(11) Å, c = 13.995(5) Å, beta = 99.62(3) degrees, and Z = 4. The anion consists of two [beta-SiNi(2)W(10)O(36)(OH)(2)(H(2)O)] Keggin moieties linked via two OH bridging groups, leading to a planar Ni(2)(OH)(2) unit. The two half-units are related by an inversion center and each contain one Ni atom in the rotated triad. The formation of the new anion involves insertion, isomerization, and dimerization. Magnetic measurements show that the central Ni(4) unit exhibits ferromagnetic (J' = 4.14 cm(-)(1)) as well as weak antiferromagnetic (J = -0.65 cm(-)(1)) Ni-Ni exchange interactions.
authors.affiliation: Institut de Réactivité, Électrochimie et Microporosités, UMR C0173, Université de Versailles, 45 Avenue des États Unis, 78035 Versailles Cedex, France, Laboratoire de Chimie des Métaux de Transition, ESA-CNRS 7071, Université Pierre et Marie Curie, 4, Place Jussieu, 75252 Paris Cedex 05, France, and Department of Physics, American University of Beirut, Bliss Street, P.O. Box 11-0236, Beirut, Lebanon.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kortz
authors.forename: Yves P.
authors.initials: YP
authors.lastname: Jeannin
authors.forename: André
authors.initials: A
authors.lastname: Tézé
authors.forename: Gilbert
authors.initials: G
authors.lastname: Hervé
authors.forename: Samih
authors.initials: S
authors.lastname: Isber