Sr4MgCr2(SO3)2 crystallizes in the tetragonal P-4m2 space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 8-coordinate geometry to four equivalent S(1), two equivalent O(1), and two equivalent O(2) atoms. In the second Sr site, Sr(2) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent O(2), and five equivalent O(3) atoms. In the third Sr site, Sr(2) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent O(2), and five equivalent O(3) atoms. Mg(1) is bonded to four equivalent S(1) atoms to form corner-sharing MgS4 tetrahedra. Cr(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form corner-sharing CrO5 square pyramids. S(1) is bonded in a 6-coordinate geometry to four equivalent Sr(1) and two equivalent Mg(1) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Cr(1) atoms to form distorted OSr4Cr2 octahedra that share corners with two equivalent O(1)Sr4Cr2 octahedra, corners with six equivalent O(3)Sr5Cr octahedra, edges with two equivalent O(1)Sr4Cr2 octahedra, faces with two equivalent O(3)Sr5Cr octahedra, and faces with four equivalent O(2)Sr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 16-55°. In the second O site, O(2) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Cr(1) atoms to form distorted OSr4Cr2 octahedra that share corners with two equivalent O(2)Sr4Cr2 octahedra, corners with six equivalent O(3)Sr5Cr octahedra, edges with two equivalent O(2)Sr4Cr2 octahedra, faces with two equivalent O(3)Sr5Cr octahedra, and faces with four equivalent O(1)Sr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 17-55°. In the third O site, O(3) is bonded to five Sr(2,2) and one Cr(1) atom to form distorted OSr5Cr octahedra that share corners with four equivalent O(3)Sr5Cr octahedra, corners with six equivalent O(1)Sr4Cr2 octahedra, corners with six equivalent O(2)Sr4Cr2 octahedra, edges with eight equivalent O(3)Sr5Cr octahedra, faces with two equivalent O(1)Sr4Cr2 octahedra, and faces with two equivalent O(2)Sr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 11-55°.
Sr4MgCr2(SO3)2 crystallizes in the tetragonal P-4m2 space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 8-coordinate geometry to four equivalent S(1), two equivalent O(1), and two equivalent O(2) atoms. All Sr(1)-S(1) bond lengths are 3.17 Å. Both Sr(1)-O(1) bond lengths are 2.55 Å. Both Sr(1)-O(2) bond lengths are 2.54 Å. In the second Sr site, Sr(2) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent O(2), and five equivalent O(3) atoms. Both Sr(2)-O(1) bond lengths are 2.77 Å. Both Sr(2)-O(2) bond lengths are 2.78 Å. There is one shorter (2.46 Å) and four longer (2.80 Å) Sr(2)-O(3) bond lengths. In the third Sr site, Sr(2) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent O(2), and five equivalent O(3) atoms. Both Sr(2)-O(1) bond lengths are 2.77 Å. Both Sr(2)-O(2) bond lengths are 2.78 Å. There is one shorter (2.46 Å) and four longer (2.80 Å) Sr(2)-O(3) bond lengths. Mg(1) is bonded to four equivalent S(1) atoms to form corner-sharing MgS4 tetrahedra. All Mg(1)-S(1) bond lengths are 2.50 Å. Cr(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form corner-sharing CrO5 square pyramids. The Cr(1)-O(3) bond length is 1.92 Å. Both Cr(1)-O(1) bond lengths are 1.99 Å. Both Cr(1)-O(2) bond lengths are 2.00 Å. S(1) is bonded in a 6-coordinate geometry to four equivalent Sr(1) and two equivalent Mg(1) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Cr(1) atoms to form distorted OSr4Cr2 octahedra that share corners with two equivalent O(1)Sr4Cr2 octahedra, corners with six equivalent O(3)Sr5Cr octahedra, edges with two equivalent O(1)Sr4Cr2 octahedra, faces with two equivalent O(3)Sr5Cr octahedra, and faces with four equivalent O(2)Sr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 16-55°. In the second O site, O(2) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Cr(1) atoms to form distorted OSr4Cr2 octahedra that share corners with two equivalent O(2)Sr4Cr2 octahedra, corners with six equivalent O(3)Sr5Cr octahedra, edges with two equivalent O(2)Sr4Cr2 octahedra, faces with two equivalent O(3)Sr5Cr octahedra, and faces with four equivalent O(1)Sr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 17-55°. In the third O site, O(3) is bonded to five Sr(2,2) and one Cr(1) atom to form distorted OSr5Cr octahedra that share corners with four equivalent O(3)Sr5Cr octahedra, corners with six equivalent O(1)Sr4Cr2 octahedra, corners with six equivalent O(2)Sr4Cr2 octahedra, edges with eight equivalent O(3)Sr5Cr octahedra, faces with two equivalent O(1)Sr4Cr2 octahedra, and faces with two equivalent O(2)Sr4Cr2 octahedra. The corner-sharing octahedral tilt angles range from 11-55°.