Sc0.43(2)Rb2Mo15S19, a partially Sc-filled variant of Rb2Mo15S19
Résumé
The structure of scandium dirubidium pentadecamolybdenum nonadecasulfide, Sc0.43 (2)Rb2Mo15S19, constitutes a partially Sc-filled variant of Rb2Mo15S19 [Picard, Saillard, Gougeon, Noel & Potel (2000), J. Solid State Chem.155, 417426]. In the two compounds, which both crystallize in the Rc space group, the structural motif is characterized by a mixture of Mo6Si8Sa6 and Mo9Si11Sa6 cluster units ('i' is inner and 'a' is apical) in a 1:1 ratio. The two components are interconnected through interunit MoS bonds. The cluster units are centred at Wyckoff positions 6b and 6a (point-group symmetries and 32, respectively). The Rb+ cations occupy large voids between the different cluster units. The Rb and the two inner S atoms lie on sites with 3. symmetry (Wyckoff site 12c), and the Mo and S atoms of the median plane of the Mo9S11S6 cluster unit lie on sites with .2 symmetry (Wyckoff site 18e). A unique feature of the structure is a partially filled octahedral Sc site with symmetry. Extended Huckel tight-binding calculations provide an understanding of the variation in the MoMo distances within the Mo clusters induced by the increase in the cationic charge transfer due to the insertion of Sc.
Domaines
Chimie théorique et/ou physique
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