Studies on Clathrasils. VI*
Abstract
Synthetic dodecasil 3C, 136 SiO2 · 16 M12 · 8 M16, is cubic with space group Fd3 and a0 = 19.402(1) Å. Structure refinement of a crystal containing M12 = N2 and small amounts of CH4 and Ar, M16 = N(CH3)3 and CO2 led to a weighted Rw = 0.064 for 883 independent reflexions. The clathrate compound is isotypic with the cubic clathrate hydrate type II.
The clathrate compound has a silica host framework with guest molecules M in two different types of cage, and it is the cubic three-layer member of the polytypic series of dodecasils. Cornersharing [SiO4] tetrahedra form a 3-dimensional 4-connected net which is built up from pseudohexagonal layers of face-sharing pentagondodecahedra ([512] cages), the fundamental cage of the dodecasil series. On connecting such layers in the sequence [unk]ABC two types of cagelike void arise, the [512] cage again and the larger [51264] cage. The guest molecules M12 and M16 which must be present during synthesis show up in difference Fourier synthesis. The entrapped molecules are oriented within the cages such that van der Waals contacts between guest molecules and host framework are optimized. The mean value of the Si – O – Si angles (174.5°) is considerably higher and the mean value of the Si – O distance (1.566 Å) considerably lower than corresponding angles and distances in silica polymorphs. If aspheric guest molecules are used during synthesis, the room temperature phase is of lower symmetry than cubic. Calorimetric and hot-stage microscope experiments with dodecasil 3C containing M16 = tetrahydrofurane show that a displacive phase transformation to the cubic high symmetry form takes place at about 110°C.
Artikel in diesem Heft
- Pyrite-type silicon diphosphide p-SiP2: Structural parameters and valence electron density distribution
- Indexing of electron double diffraction patterns from partially-decomposed cadmium halide crystals
- The refinement of unit cell parameters from two-circle diffractometer measurements
- The crystal structure of acenaphte (9,10b) quinolizinium-13-ethoxycarbonyl bromide sesquihydrate [(C22H16NO2)+Br−.1.5H2O]
- One-phase seminvariants of first rank
- Estimation of the electrooptic Kerr effect in ADP and DKDP crystals*
- Korrektur des Absorptionsfaktors für eine ebene, undurchlässige Pulverplatte und zum symmetrischen Braggfall analogen Strahlengang
- Molecular and crystal structure of C.I. Pigment Yellow 1. 11680, N-Phenyl-2-(4-methyl-2-nitro-phenyl-hydrazono)-3-oxo-butyramide (Hansagelb G)
- Studies on Clathrasils. VI*
- Die Kristallstruktur des Cs7Ca4(N3)15
- SYMOP – an improved computer program for the derivation of symmetry operations from the space-group symbols
- The structural properties of synthetic Sr-gehlenite, Sr2Al2SiO7
- Crystal structure of Sb2MoO6
- The collinear antiferromagnetic structure of EuSb2, a neutron diffraction study
- Molecular and crystal structure of cyanoformamide
- Preparation and structure of LaCo8P5
- Crystal structure data of three model urethanes*
- |(1,2-Bis(diphenylphosphino)ethane) (2,4-pentanedionato) Nickel (II)| tetraphenylborate
Artikel in diesem Heft
- Pyrite-type silicon diphosphide p-SiP2: Structural parameters and valence electron density distribution
- Indexing of electron double diffraction patterns from partially-decomposed cadmium halide crystals
- The refinement of unit cell parameters from two-circle diffractometer measurements
- The crystal structure of acenaphte (9,10b) quinolizinium-13-ethoxycarbonyl bromide sesquihydrate [(C22H16NO2)+Br−.1.5H2O]
- One-phase seminvariants of first rank
- Estimation of the electrooptic Kerr effect in ADP and DKDP crystals*
- Korrektur des Absorptionsfaktors für eine ebene, undurchlässige Pulverplatte und zum symmetrischen Braggfall analogen Strahlengang
- Molecular and crystal structure of C.I. Pigment Yellow 1. 11680, N-Phenyl-2-(4-methyl-2-nitro-phenyl-hydrazono)-3-oxo-butyramide (Hansagelb G)
- Studies on Clathrasils. VI*
- Die Kristallstruktur des Cs7Ca4(N3)15
- SYMOP – an improved computer program for the derivation of symmetry operations from the space-group symbols
- The structural properties of synthetic Sr-gehlenite, Sr2Al2SiO7
- Crystal structure of Sb2MoO6
- The collinear antiferromagnetic structure of EuSb2, a neutron diffraction study
- Molecular and crystal structure of cyanoformamide
- Preparation and structure of LaCo8P5
- Crystal structure data of three model urethanes*
- |(1,2-Bis(diphenylphosphino)ethane) (2,4-pentanedionato) Nickel (II)| tetraphenylborate
