title: Di- and tri-cobalt silicotungstates: synthesis, characterization, and stability studies.
abstract: Di- and tricobalt silicotungstate complexes, K(5)Na(4)H(4)[{Na(3)(μ-OH(2))(2)Co(2)(μ-OH)(4)} (Si(2)W(18)O(66))]·37H(2)O (1) and K(6)Na(3)[Na(H(2)O){Co(H(2)O)(3)}(2){Co(H(2)O)(2)}(Si(2)W(18)O(66))]·22H(2)O (2), have been synthesized through reaction of cobalt chloride and [A-α-SiW(9)O(34)](10-) in acidic buffer solution. They have been characterized by X-ray crystallography, elemental analysis, cyclic voltammetry, infrared, and UV-vis spectroscopy. In 1, two cobalt atoms as well as three sodium atoms are incorporated in the central pocket of the [Si(2)W(18)O(66)](16-) polyanion. In 2, one cobalt atom and one sodium atom are incorporated in the pocket of [Si(2)W(18)O(66)](16-); two other cobalt atoms in this complex protrude outside the pocket and connect with WO(6) units of other [Si(2)W(18)O(66)](16-) polyanions to form a one-dimensional polymeric structure. The crucial parameters in the synthesis of these two compounds are discussed, and their stability in different buffer solutions is studied. The decomposition of 1 or 2 in heated potassium acetate buffer (pH 4.8, 1 M) yields K(11)[{Co(2)(H(2)O)(8)}K(Si(2)W(18)O(66))]·17H(2)O (3) based on spectroscopic studies and an X-ray crystal structure.
authors.affiliation: Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States.
authors.forename: Guibo
authors.initials: G
authors.lastname: Zhu
authors.forename: Yurii V
authors.initials: YV
authors.lastname: Geletii
authors.forename: Jie
authors.initials: J
authors.lastname: Song
authors.forename: Chongchao
authors.initials: C
authors.lastname: Zhao
authors.forename: Elliot N
authors.initials: EN
authors.lastname: Glass
authors.forename: John
authors.initials: J
authors.lastname: Bacsa
authors.forename: Craig L
authors.initials: CL
authors.lastname: Hill