Derivatization of the Rhombohedral Rare-Earth-Metal (R) Cluster Halides R7(Z)X12: The New NaLa6(Os)I12
✍ Scribed by S. Uma; John D. Corbett
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 428 KB
- Volume
- 161
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
The many examples of R 7 (Z)X 12 cluster phases for R ؍ rareearth metal, Z ؍ interstitial element, X ؍ Cl, Br, I, occur in a characteristic rhombohedral structure R 3؉ [R 6 (Z)X 12 ] in which the seventh R atom is situated in a trigonal antiprismatic X i site between halide-interbridged clusters in an anionic network that can be described as [La 6 (Os)]X i 6 X i؊a 6 X a؊i 6 ]. The 5rst example of a substituted derivative, NaLa 6 (Os)I 12 , has been achieved via exploratory synthetic reactions in neat systems near 8503C. The structure has been re5ned in space group R3 (No. 148), a ؍ 16.214(4) A > , c ؍ 11.172(4) A > , R/R w (F) ؍ 3.5/3.9%. The cluster is geometrically very close to an ideal octahedron in shape, showing a trigonal elongation of only 0.026(3) A > and La+Os+La angles of 90 ؎ 0.37(4)3. The La+I and Na+I distances are likewise very similar and substantially ideal. This regularity is unexpected in view of both the cluster:s apparent 15-cluster-based electron con5guration with an expected nominal t 3 1u HOMO and the behavior of many other cluster structures with incomplete electronic structures. Furthermore, the phase inexplicably exhibits only a TIP term in magnetic susceptibility, &3.4؋ 10 ؊4 emu mol ؊1 , for which no explanation is currently available. 2001 Academic Press