Similar K@Au10Sn10 Polyhedra in the Markedly Different Structures of KAu4Sn6 and KAu3Sn3. Syntheses and Characterization
These compounds were synthesized by high-temperature reactions of the elements in welded Ta tubes and characterized by X-ray diffraction methods and linear muffin-tin orbital (LMTO) calculations. AAu{sub 4}Sn{sub 6} (A = K, Rb) have a new structural type (Fddd, Z = 8), and KAu{sub 3}Sn{sub 3} (Pmmn, Z = 2) is isostructural with SrAu{sub 3}In{sub 3}. Both orthorhombic structures contain similar condensed K{at}Au{sub 10}Sn{sub 10} polyhedral building blocks, which can be described as overall 6-8-6 arrangements of planar rings or, alternatively, as hexagonal prisms centered by K and augmented about the waists by 8-rings of Au and Sn. However, the 3D Au-Sn networks differ appreciably in both composition and the modes of condensation. In KAu{sub 3}Sn{sub 3}, the prisms stack by sharing both hexagonal faces with like neighbors along a, whereas those in KAu{sub 4}Sn{sub 6} condense in a complex zigzag network. Compared with related indium systems, the structure change from KAu{sub 4}In{sub 6} (P{sub 6}m2, Z = 1) to KAu{sub 4}Sn{sub 6} apparently illustrates the effect of complex factors such as atom size and valence electron counts on structure, whereas the SrAu{sub 3}In{sub 3} and KAu{sub 3}Sn{sub 3} pair are isotypic. Both compounds are Pauli-paramagnetic and inert to water at room temperature for several days. Tight-binding electronic structure (LMTO) calculations emphasize the dominance and strength of the heteroatomic Au-Sn bonding.
- Research Organization:
- Ames Lab., Ames, IA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC02-07CH11358
- OSTI ID:
- 977052
- Report Number(s):
- IS-J 7442; TRN: US201009%%189
- Journal Information:
- Inorganic Chemistry, Vol. 47, Issue 9
- Country of Publication:
- United States
- Language:
- English
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