Données cristallographiques sur le tétrachromate d'ammonium (NH₄)₂Cr₄O₁₃

Abstract

(NH4)2Cr4O13 is monoclinic (P21/c, isotypic with K2Cr4O13 and Rb2Cr4O13, with a = 17.82 (1), b = 7.658 (4), c = 9.360 (3) Å, β = 92.00 (1)° , V = 1276 Å3, Z = 4 and Dx = 2.35 Mg/m3.

1,4-Diazabicyclo[2.2.2]octane-1,4-diium trichromate

“…As indicated by the obvious differences between the magnitudes of the CrÐO b and CrÐO t distances, as well the great disparity between the values of the OÐCrÐ O angles, the coordination geometries formed by the four O atoms around the Cr atom are distorted tetrahedra. These results are in good agreement with those reported for Rb 2 Cr 3 O 10 (Blum, 1979a), (NH 4 ) 2 Cr 3 O 10 (Blum, 1979b;Blum & Guitel, 1980), K 2 Cr 3 O 10 (Blum et al, 1979), dipyrazinium trichromate (Pressprich et al, 1988), tetramethylammonium trichromate (Fosse  et al, 2001) and -Cs 2 Cr 3 O 10 ( Kolitsch, 2003). The title compound exhibits dissimilar CrÐOÐCr angles [127.34 (12) and 132.80 (12) ;…”

Structures of mercury dichloride–dipotassium dichromate (1/1), HgCl2.K2Cr2O7, and mercury dichloride–diammonium dichromate (1/1), HgCl2.(NH4)2Cr2O7

“…These two adduct compounds were described as early as 1859 (Groth) but up to now never investigated from a structural point of view. This work is part of the investigation of condensed chromic anions: (CrnO3n+l) 2 (Durif & Averbuch-Pouchot, 1979;Blum & Tran Qui, 1979;Blum, AverbuchPouchot & Guitel, 1979;.…”

Cs2Cr4O13: a new structure type among alkali tetrachromates

“…Cs 2 Cr 4 O 13 exhibits a structure type that is new among alkali tetrachromates. However, the three structurally characterized chemical analogs Rb 2 Cr 4 O 13 (Lo È fgren, 1971(Lo È fgren, , 1973, K 2 Cr 4 O 13 [Lo È fgren (unpublished) cited by Blum & Tran Qui (1979)] and (NH 4 ) 2 Cr 4 O 13 (Blum & Tran Qui, 1979), which are all isotypic (monoclinic, space group P2 1 /c, with a 9 17.8 A Ê , b 9 7.7 A Ê , c 9 9.4 A Ê and 9 92 ), contain [Cr 4 O 13 ] 2À anions with similar zigzag-like structures. Only the mutual arrangement between these anions and the alkali cations is different (Fig.…”