Darstellung und Aufbau der Lanthanoidfluorid‐catena‐Trisilicate M3F[Si3O10] (M = Dy,Ho, Er) im Fluorthalenit‐Typ (Y3F[Si3O10]) |
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Authors: | Helge Müller‐Bunz Thomas Schleid |
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Abstract: | Synthesis and Constitution of Fluorothalenite‐Type (Y3FSi3O10]) Fluoride catena‐ Trisilicates M3FSi3O10] with the Lanthanides (M = Dy, Ho, Er) By the reaction of the sesquioxides M2O3 with the corresponding trifluorides MF3 (M = Dy, Ho, Er), SiO2 and CsCl as flux (molar ratio: 1 : 1 : 3 : 6; 700 °C, 7 d) in evacuated silica tubes and gastight sealed metal capsules made of platinum, niobium or tantalum, respectively, single crystals of the fluoride silicates M3FSi3O10] (monoclinic, P21/n; Z = 4; M = Dy: a = 734.06(6), b = 1116.55(9), c = 1040.62(8) pm, β = 97.281(7)°; M = Ho: a = 730.91(6), b = 1111.68(9), c = 1037.83(8) pm, β = 97.238(7)°; M = Er: a = 727.89(6), b = 1107.02(9), c = 1035.21(8) pm, β = 97.209(7)°) were obtained. The most important building groups in the crystal structures of the thalenite type are “isolated” FM3]8+ triangles and catena‐trisilicate anions Si3O10]8–, which contain three SiO4] tetrahedra linked to a chain fragment via common corners. This has the shape of a horseshoe where both the terminal tetrahedra show different conformations (eclipsed and staggered) relative to the central unit. Therefore a chelatizing coordination on the same M3+ cation via oxygen atoms of both terminal SiO4] groups is possible. The narrow area of existence of these fluoride silicates within the lanthanide series will be discussed and structural comparisons with other catena‐trisilicates are presented. |
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Keywords: | Lanthanides Silicates Fluoride catena‐trisilicates Crystal structure |
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