Crystal structure and thermal analysis of the tetramethylammonium dichromate and trichromate

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) ;…”

Bis(2,6-dimethylpyridinium) dichromate

“…The shorter distances correspond to double bonds and the longer distances to single bonds. They are in good agreement with those found in bipyridinium dichromate (Martín-Zarza et al, 1995), bis(-octyltrimethylammonium) dichromate (Fossé et al, 1998) and tetramethylammonium dichromate (Fossé et al, 2001). The coordination geometry of each Cr atom is distorted tetrahedral.…”

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

“…Therefore, the coordination geometries formed by the four O atoms around each Cr atom are distorted tetrahedra. The bond lengths and angles are in good agreement with those found in bipyridinium dichromates (Martõ Ân-Zarza et al, 1995), bis(octyltrimethylammonium) dichromate (Fosse  et al, 1998) and tetramethylammonium dichromate (Fosse  et al, 2001). (CrO 3 ) n is an extreme case of a polychromate, where chains of corner-sharing CrO 4 tetrahedra extend along the whole crystal (Stephens & Cruickshank, 1970).…”