76 research outputs found
Metastable Se6 as a ligand for Ag+: from isolated molecular to polymeric 1D and 2D structures
Attempts to prepare the hitherto unknown Se6 2+ cation by the reaction of elemental selenium and Ag[A] ([A]- = [Sb(OTeF5)6]-, [Al(OC(CF3)3)4]-) in SO2 led to the formation of [(OSO)Ag(Se6)Ag(OSO)][Sb(OTeF5)6]2 1 and [(OSO)2Ag(Se6)Ag(OSO)2][Al(OC(CF3)3)4]2 2a. 1 could only be prepared by using bromine as co-oxidant, however, bulk 2b (2a with loss of SO2) was accessible from Ag[Al(OC(CF3)3)4] and grey Se in SO2 (chem. analysis). The reactions of Ag[MF6] (M= As, Sb) and elemental selenium led to crystals of 1/â{[Ag(Se6)]â[Ag2(SbF6)3]â} 3 and {1/â[Ag(Se6)Ag]â}[AsF6]2 4. Pure bulk 4 was best prepared by the reaction of Se4[AsF6]2, silver metal and elemental selenium. Attempts to prepare bulk 1 and 3 were unsuccessful. 1â4 were characterized by single-crystal X-ray structure determinations, 2b and 4 additionally by chemical analysis and 4 also by X-ray powder diffraction, FT-Raman and FT-IR pectroscopy. Application of the PRESTO III sequence allowed for the first time 109Ag MAS NMR investigations of 4 as well as AgF, AgF2, AgMF6 and {1/â[Ag(I2)]â}[MF6] (M= As, Sb). Compounds 1 and 2a/b, with the very large counter ions, contain isolated [Ag(Se6)Ag]2+ heterocubane units consisting of a Se6 molecule bicapped by two silver cations (local D3d sym). 3 and 4, with the smaller anions, contain close packed stacked arrays of Se6 rings with Ag+ residing in octahedral holes. Each Ag+ ion coordinates to three selenium atoms of each adjacent Se6 ring. 4 contains [Ag(Se6)+]â stacks additionally linked by Ag(2)+ into a two dimensional network. 3 features a remarkable 3-dimensional [Ag2(SbF6)3]- anion held together by strong SbâF ⌠Ag contacts between the component Ag+ and [SbF6]- ions. The hexagonal channels formed by the [Ag2(SbF6)3]- anions are filled by stacks of [Ag(Se6)+]â cations. Overall 1â4 are new members of the rare class of metal complexes of neutral main group elemental clusters, in which the main group element is positively polarized due to coordination to a metal ion. Notably, 1 to 4 include the commonly metastable Se6 molecule as a ligand. The structure, bonding and thermodynamics of 1 to 4 were investigated with the help of quantum chemical calculations (PBE0/TZVPP and (RI-)MP2/TZVPP, in part including COSMO solvation) and BornâFajansâHaber-cycle calculations. From an analysis of all the available data it appears that the formation of the usually metastable Se6 molecule from grey selenium is thermodynamically driven by the coordination to the Ag+ ions
ChemInform Abstract: Methanolothermal Synthesis and Crystal Structure of Tetraselenidoarsenates(V) and -antimonates(V) of Rubidium and Cesium.
ChemInform Abstract: RbAg2As3Se6: A Unique Three-Dimensional Silver-Selenoarsenate Framework 3â [Ag2As3Se6]-, Assembled from [As3Se6]3- Rings and âAg2+2â Dumbbell Units.
ChemInform Abstract: Mesostructured Non-oxidic Solids with Adjustable Worm-Hole Shaped Pores: M-Ge-Q (Q: S, Se) Frameworks Based on Tetrahedral [Ge4Q10]4- Clusters.
ChemInform Abstract: Cs3AgAs4Se8 and CsAgAs2Se4: Selenoarsenates with Infinite 1â[AsSe2]- Chains in Different Ag+ Coordination Environments.
ChemInform Abstract: Cs4BiAs3Se7: A Novel Bismuth-Selenoarsenate with Infinite â1[BiAs3Se7]4- Chains Containing Two Different Anions, [AsSe3]3- and trans-[As2Se4]4-.
Surfactant-Templated Inorganic Lamellar and Non-Lamellar Hybrid Phases Containing Adamantane [Ge 4
Methanolothermal Synthesis and Structures of the Quaternary Group 14 - Group 15 Cesium Selenidometalates Cs3AsGeSe5 and Cs4Ge2Se6
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