Interstitial atoms in metal-metal bonded arrays: the synthesis and characterization of heptascandium decachlorodicarbide, Sc/sub 7/Cl/sub 10/C/sub 2/, and comparison with the interstitial-free Sc/sub 7/Cl/sub 10/
Reaction of Sc strips, ScCl/sub 3/, and graphite at 860-1000/sup 0/C gives Sc/sub 7/Cl/sub 10/C/sub 2/ in quantitative yields, with transport occurring at the higher temperatures; adventitious carbon will also produce the phase. The compound has been shown to be isostructural with Er/sub 7/I/sub 10/ by single-crystal X-ray diffraction (a = 18.620 (4) A, b = 3.4975 (6) A, c = 11.810 (2) A, ..beta.. = 99.81 (2)/sup 0/; space group C2/m, Z = 2, R = 0.029, R/sub w/ = 0.046 for 676 reflections, MoK..cap alpha.., 2 theta < 50/sup 0/). The phase contains double chains of condensed scandium octahedra sharing edges with a carbon approximately centered in each (anti d(Sc-C) = 2.31 A) together with isolated scandium atoms in a parallel chain of chloride octahedra. The arrangement is very similar to that in the previously known Sc/sub 7/Cl/sub 10/, from which the heavy atom arrangement can be derived by displacement of all metal atoms by b/2 so as to convert chlorine functions on the metal chain from face-capping to edge-bridging. The driving force for this is thought to be the reduction of carbon-chlorine repulsive interactions. Core and valence x-ray photoelectron spectra (XPS) for Sc/sub 7/Cl/sub 10/, Sc/sub 7/Cl/sub 10/Cl/sub 2/, Sc/sub 2/Cl/sub 2/C, ScCl/sub 3/, and Sc are presented to demonstrate the appearance of a carbide-like state for the interstitial, the presence of two different types of scandium in the first two compounds, the oxidation of the chain that accompanies the carbon insertion, and a substantial Sc-C covalency. The latter arises through mixing of the interstitial's 2s and 2p valence orbitals with metal-metal bonding cluster orbitals of the same symmetry. 37 references, 6 figures, 7 tables.
- Research Organization:
- Iowa State Univ., Ames
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 5495640
- Report Number(s):
- CONF-840415-; TRN: 85-019166
- Journal Information:
- J. Solid State Chem.; (United States), Vol. 57:1; Conference: 187. national meeting of the American Chemical Society, St. Louis, MO, USA, 8 Apr 1984
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBIDES
CHEMICAL PREPARATION
X-RAY DIFFRACTION
CHLORINE COMPOUNDS
SCANDIUM COMPOUNDS
BOND LENGTHS
CRYSTAL LATTICES
EXPERIMENTAL DATA
LATTICE PARAMETERS
MONOCRYSTALS
SPACE GROUPS
STRUCTURAL CHEMICAL ANALYSIS
VALENCE
VERY HIGH TEMPERATURE
CARBON COMPOUNDS
COHERENT SCATTERING
CRYSTAL STRUCTURE
CRYSTALS
DATA
DIFFRACTION
DIMENSIONS
HALOGEN COMPOUNDS
INFORMATION
LENGTH
NUMERICAL DATA
SCATTERING
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
400201 - Chemical & Physicochemical Properties