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1998 (1)
1980 (1)
1Author    Armin Weiss, Gerd Beil, Heinrich MeyerRequires cookie*
 Title    The Topochemical Reaction of CaSi2 to a Two-Dimensional Subsiliceous Acid Si6H3(OH)3 (= Kautskys' Siloxene)  
 Abstract    Kautsky's siloxene was prepared in a topochemical reaction from large crystals of CaSi2. The structure model was revised. Siloxene is a subsiliceous acid [Sie]H3(OH)3 and consists of two-dimensional corrugated Si-layers with three Si-Si bonds per silicon and an OH-or H-ligand, respectively. Ordering of adjacent layers is turbostratic. The layer lattice is capable of forming intercalation complexes. On intercalation only the layer distance is changed. The alkoxylated derivatives Si6H3(OCH3)3" and Si6H3(OC2H5)3" are also able to inter-calate polar molecules. 
  Reference    (Z. Naturforsch. 35b, 25—30 [1980]; eingegangen am 24. August 1979) 
  Published    1980 
  Keywords    Topochemical Reaction, Calciumdisilicide, Subsiliceous Acid, Siloxene, Intercalation Reactions 
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 TEI-XML for    default:Reihe_B/35/ZNB-1980-35b-0025.pdf 
 Identifier    ZNB-1980-35b-0025 
 Volume    35 
2Author    Francoanellite K^alschpo^cpo, Stefan Dicka, Thomas ZeiskebRequires cookie*
 Title    Francoanellit K3A15HP04)6(P04)2*12H20: Struktur und Synthese durch topochemische Entwässerung von Taranakit-I 2 H2O: Structure and Synthesis by Topochemical Dehydration of Taranakite  
 Abstract    Single crystals of synthetic francoanellite K3Al5(HP0 4)6(P0 4)2-12H20 could be obtained for the first time by topochemical dehydration of taranakite crystals. An X-ray structure de­ termination showed francoanellite to be the mineral with the second longest crystallographic axis described hitherto. Crystal data: space group R3c, a = 869.0(2), c = 8227(1)pm, Z = 6 , R g = 0.042. Francoanellite is a layer structure mineral having six layers of composition [K3Al5(HP04)6(P04)2(H2 0)i2], connected by hydrogen bonds. The rigid layer is formed by columns of corner sharing hydrogen phosphate tetrahedra and AIOö-octahedra which are inter­ connected by additional six-coordinated A1 ions. In trigonal holes of the layer orthophosphate ions are situated. The structure of francoanellite is very similar to the structure of taranakite K3H6Al5(P04)8-18H20 which has planar water interlayers between the Al-phosphate layers. A neutron scattering experiment with subsequent Rietveld refinement of the powder pattern gave the H-atom positions. Hydrogen bonds in francoanellite are formed within the rigid layers and between them. During the reaction taranakite —► francoanellite crystals in an intermediate stage of dehy­ dration could be obtained. From the c-axis of 8858 pm and one-dimensional electron density projections it can be proposed that in these crystals every second water interlayer was lost and a first order staging product of the deintercalation of water from taranakite was formed. 
  Reference    Z. Naturforsch. 53b, 711—719 (1998); eingegangen am 2. März 1998 
  Published    1998 
  Keywords    Crystal Structure, Neutron Scattering, Francoanellite, Taranakite, Topochemical Reaction 
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 TEI-XML for    default:Reihe_B/53/ZNB-1998-53b-0711.pdf 
 Identifier    ZNB-1998-53b-0711 
 Volume    53