NaCr12(Si2O7)4Br crystallizes in the tetragonal I4mm space group. The structure consists of two hydrogen bromide atoms inside a NaCr12(Si2O7)4 framework. In the NaCr12(Si2O7)4 framework, Na(1) is bonded in a distorted square co-planar geometry to four equivalent O(5) atoms. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(3) atoms. In the second Cr site, Cr(2) is bonded in a square co-planar geometry to two equivalent O(2) and two equivalent O(4) atoms. In the third Cr site, Cr(3) is bonded in a square co-planar geometry to two equivalent O(3) and two equivalent O(4) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(5), and two equivalent O(4) atoms to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(2), one O(5), and two equivalent O(3) atoms to form corner-sharing SiO4 tetrahedra. There are five inequivalent O sites. In the first O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Si(1), and one Si(2) atom. In the second O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Cr(1) and one Si(1) atom. In the third O site, O(2) is bonded in a trigonal planar geometry to two equivalent Cr(2) and one Si(2) atom. In the fourth O site, O(3) is bonded in a distorted trigonal planar geometry to one Cr(1), one Cr(3), and one Si(2) atom. In the fifth O site, O(4) is bonded in a distorted trigonal planar geometry to one Cr(2), one Cr(3), and one Si(1) atom.
NaCr12(Si2O7)4Br crystallizes in the tetragonal I4mm space group. The structure consists of two hydrogen bromide atoms inside a NaCr12(Si2O7)4 framework. In the NaCr12(Si2O7)4 framework, Na(1) is bonded in a distorted square co-planar geometry to four equivalent O(5) atoms. All Na(1)-O(5) bond lengths are 2.46 Å. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(3) atoms. Both Cr(1)-O(1) bond lengths are 2.06 Å. Both Cr(1)-O(3) bond lengths are 2.07 Å. In the second Cr site, Cr(2) is bonded in a square co-planar geometry to two equivalent O(2) and two equivalent O(4) atoms. Both Cr(2)-O(2) bond lengths are 2.05 Å. Both Cr(2)-O(4) bond lengths are 2.06 Å. In the third Cr site, Cr(3) is bonded in a square co-planar geometry to two equivalent O(3) and two equivalent O(4) atoms. Both Cr(3)-O(3) bond lengths are 2.05 Å. Both Cr(3)-O(4) bond lengths are 2.05 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(5), and two equivalent O(4) atoms to form corner-sharing SiO4 tetrahedra. The Si(1)-O(1) bond length is 1.64 Å. The Si(1)-O(5) bond length is 1.68 Å. Both Si(1)-O(4) bond lengths are 1.65 Å. In the second Si site, Si(2) is bonded to one O(2), one O(5), and two equivalent O(3) atoms to form corner-sharing SiO4 tetrahedra. The Si(2)-O(2) bond length is 1.64 Å. The Si(2)-O(5) bond length is 1.68 Å. Both Si(2)-O(3) bond lengths are 1.65 Å. There are five inequivalent O sites. In the first O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Si(1), and one Si(2) atom. In the second O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Cr(1) and one Si(1) atom. In the third O site, O(2) is bonded in a trigonal planar geometry to two equivalent Cr(2) and one Si(2) atom. In the fourth O site, O(3) is bonded in a distorted trigonal planar geometry to one Cr(1), one Cr(3), and one Si(2) atom. In the fifth O site, O(4) is bonded in a distorted trigonal planar geometry to one Cr(2), one Cr(3), and one Si(1) atom.