title: High-temperature, high-pressure hydrothermal synthesis, crystal structure, and solid state NMR spectroscopy of a new vanadium(IV) silicate: Rb(2)(VO)(Si(4)O(10)).xH(2)O.
abstract: A new vanadium(IV) silicate, Rb(2)(VO)(Si(4)O(10)).xH(2)O (x approximately 0.1), has been synthesized by a high-temperature, high-pressure hydrothermal method. It crystallizes in the tetragonal space group I4(1)md (No. 109) with a = 12.2225(7) A, c = 7.7948(6) A, and Z = 4. The structure consists of spiral chains of corner-sharing SiO(4) tetrahedra linked to neighboring chains via corner sharing to form a 3-D silicate framework which delimits channels to accommodate the VO(2+) groups. The Rb(+) ions are located in the cavities within the silicate framework. Magnetic susceptibility confirms the valence of vanadium. A partially occupied lattice water site is confirmed by IR and solid state (1)H NMR spectroscopy. The structure of the title compound is considerably different from those of the synthetic silicate K(2)(VO)(Si(4)O(10)).H(2)O and the two polymorphs of the natural mineral Ca(VO)(Si(4)O(10)).4H(2)O, although they have identical framework stoichiometry.
authors.affiliation: Department of Chemistry, National Central University, Chungli, and Institute of Chemistry, Academia Sinica, Taipei, Taiwan, R.O.C.
authors.forename: Chun-Yi
authors.initials: CY
authors.lastname: Li
authors.forename: Chan-Yen
authors.initials: CY
authors.lastname: Hsieh
authors.forename: Hsiu-Mei
authors.initials: HM
authors.lastname: Lin
authors.forename: Hsien-Ming
authors.initials: HM
authors.lastname: Kao
authors.forename: Kwang-Hwa
authors.initials: KH
authors.lastname: Lii