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Berichtigung zur Arbeit :Die Kristallstruktur von Cs,PrO,, sowie uber Cs,Ce03, Cs,TbO,, Rb,CeO, und Rb2Tb0,

Erstmals erhalten wurden farblose Einkristalle von Li8SnO6 [Gemenge von Li2O/SnO2; Li: Sn 8,8:1 bis 30:1; Ni‐Bömbchen; 1 000°C; 6 Wochen]. Li8SnO6 kristallisiert trigonal‐rhomboedrisch R3C 3i2 mit a = 5,461, c = 15,278 Å, Z = 3, Sn in 3(a),  Li| in 18(f),  Li‖ in 6(c) und O in 18(f) (Parameter s. Text). Es ist R = 3,37%, R′ = 3,74% (197 0kl–3kl, MoKα, Diffraktometerdaten). Der Madelunganteil der Gitterenergie MAPLE und die Effektiven Koordinationszahlen ECoN werden berechnet und diskutiert, die Tendenz zur interlamellaren Verzwilligung nach (001) erklärt.

Overhauser effect at 7-H and a still noticeable effect at 1'-H. Hence compound (1) has C-7-(S) chirality, while (2) is the (R)-diastereomer.As can be deduced from the coupling constants (Table 2) the non-reducing glucose ring in ( 1 ) and (2), which together with the condensed 1.3-dioxane ring forms a trans-trioxadecalin system, is present in a 4Cl chair conformation. Only the 31.2. coupling constant (8.8Hz) is greater than in normal disaccharides, presumably as a result of the condensed eightmembered ring. The reducing glucose ring also shows a definite 4Cl chair conformation; but only in the case of (I) is a noticeably reduced transdiaxial coupling constant (J3,4 = 7.8Hz) observed.According to studies with Dreiding models the 1,3,6-trioxacyclooctane structural unit in both (1) and (2) can be present in rigid twisted conformations or flexible "tub-chair'' conformations, while butterfly ("tub-tub") or crown ("chair-chair") conformation^ [^] can be ruled out. Determination of the relative positions of the p,1+4-linked saccharides revealed the torsion angles i'-H, C-If, C-4, 0 -4 (0,) and C-i', 0-4, C-4, 4-H ( 0 2 ) of e1=120" and 02=300[61. Measurements on a model of the "tub-chair'' conformation gave for (1) elzO" and €I2 z 150--180", consistent with an highly stretched molecule. In the case of (2) the corresponding torsional angles are 0' z 150-180" and O 2~O 0 , resulting in a sickle-shaped molecule, as confirmed by X-ray structure analysis['! Thus, in each case the eight-membered ring system of the isomers (I) and (2) assumes a "chair-tub'' or a "tub-chair'' conformation, determined by the fixed chair conformations of the saccharide molecules.

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