The First Oxostannate(II): K₂Sn₂O₃

Abstract

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.

Defect Antiperovskite Compounds Hg3Q2I2 (Q = S, Se, and Te) for Room-Temperature Hard Radiation Detection

“…Assuming that the [QHg 3 ] 4+ pyramids are part of incomplete [QHg 3 □ 3 ] 4+ octahedra (where □ denotes a vacancy), the crystal structure of the Hg 3 Q 2 X 2 compounds can be described as a defective antiperovskite with an idealized formula “Hg 6 Q 2 X 2 ” in which 50% of the Hg atoms are missing to produce the Hg 3 □ 3 Q 2 X 2 composition (see Figure ). A similar structure is also adopted in defect perovskite K 2 Sn 2 O 3 and recently reported defect antiperovskite Fe 2 SeO, where 1/2 of anions and 1/3 of cations are missing, respectively. The structure evolution of [Hg 3 Q 2 ] motifs plays an important role in determining the physical properties of these materials as indicated in the following discussion.…”

Design of ternary alkaline-earth metal Sn(ii) oxides with potential good p-type conductivity

“…The overwhelming majority of low-lying energy structures are found to contain Sn coordinated by three O atoms (in red). This resembles that of A 2 Sn 2 O 3 (A = Na, K, Rb and Cs) [30,31], but is distinct from that of the litharge SnO where Sn is four-fold coordinated by O. The changes in local chemical bondings between Sn and O cause deviation of electronic structure in ternary Sn(II) oxides from that in binary SnO (see below).…”

“…[29] Ternary oxides containing Sn(II) have been less studied. The known materials of oxostannates, e.g., A 2 Sn 2 O 3 (A = Na, K, Rb and Cs) [30,31], having rather low calculated hole effective mass and band gaps of 2.4-2.7 eV, were recently proposed as promising p-type TCO. [10] However, the compounds containing alkali metals are prone to hydrolysis on exposure to air [30], and are meanwhile may not be fully compatible with semiconductor based devices.…”

Structural, Electronic, and Optical Properties of K2Sn3O7 with an Offset Hollandite Structure

“…The K–Sn–O system contains five phases with known crystal structures. There are two Sn 4+ compounds K 2 SnO 3 and K 4 SnO 4 , , as well as the Sn 2+ compounds K 2 SnO 2 , K 2 Sn 2 O 3 , and K 4 SnO 3 . − Tournoux performed the only systematic phase equilibria study on this system . His elemental analysis of a K 2 SnO 3 decomposition product revealed an estimated stoichiometry K 2 Sn 3 O 7 , but the structure was never solved.…”