MgCr3(SO4)6 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 3-coordinate geometry to one O(6), one O(7), and one O(9) atom. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(11), one O(12), one O(15), one O(20), one O(3), and one O(8) atom to form CrO6 octahedra that share  a cornercorner with one S(1)O4 tetrahedra;  a cornercorner with one S(2)O4 tetrahedra;  a cornercorner with one S(3)O4 tetrahedra;  a cornercorner with one S(5)O4 tetrahedra; and corners with two equivalent S(4,6)O4 tetrahedra. In the second Cr site, Cr(2) is bonded to one O(16), one O(18), one O(19), one O(21), one O(23), and one O(24) atom to form CrO6 octahedra that share  a cornercorner with one S(1)O4 tetrahedra;  a cornercorner with one S(2)O4 tetrahedra;  a cornercorner with one S(3)O4 tetrahedra;  a cornercorner with one S(5)O4 tetrahedra; and corners with two equivalent S(4,6)O4 tetrahedra. In the third Cr site, Cr(3) is bonded to one O(10), one O(13), one O(14), one O(17), one O(22), and one O(5) atom to form CrO6 octahedra that share  a cornercorner with one S(1)O4 tetrahedra;  a cornercorner with one S(2)O4 tetrahedra;  a cornercorner with one S(3)O4 tetrahedra;  a cornercorner with one S(5)O4 tetrahedra; and corners with two equivalent S(4,6)O4 tetrahedra. There are five inequivalent S sites. In the first S site, S(1) is bonded to one O(24), one O(3), one O(5), and one O(6) atom to form SO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra, and  a cornercorner with one Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-42°. In the second S site, S(2) is bonded to one O(13), one O(21), one O(7), and one O(8) atom to form SO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra, and  a cornercorner with one Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-42°. In the third S site, S(3) is bonded to one O(14), one O(15), one O(23), and one O(9) atom to form SO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra, and  a cornercorner with one Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-42°. In the fourth S site, S(4,6) is bonded to one O(10), one O(11), one O(16), and one O(2) atom to form SO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra, and  a cornercorner with one Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-53°. In the fifth S site, S(5) is bonded to one O(12), one O(17), one O(18), and one O(4) atom to form SO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra, and  a cornercorner with one Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-53°. There are twenty-four inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one S(4,6) atom. In the second O site, O(2) is bonded in a single-bond geometry to one S(4,6) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Cr(1) and one S(1) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one S(5) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Cr(3) and one S(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Mg(1) and one S(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Mg(1) and one S(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Cr(1) and one S(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Mg(1) and one S(3) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Cr(3) and one S(4,6) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Cr(1) and one S(4,6) atom. In the twelfth O site, O(12) is bonded in a bent 150 degrees geometry to one Cr(1) and one S(5) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Cr(3) and one S(2) atom. In the fourteenth O site, O(14) is bonded in a bent 150 degrees geometry to one Cr(3) and one S(3) atom. In the fifteenth O site, O(15) is bonded in a bent 150 degrees geometry to one Cr(1) and one S(3) atom. In the sixteenth O site, O(16) is bonded in a bent 120 degrees geometry to one Cr(2) and one S(4,6) atom. In the seventeenth O site, O(17) is bonded in a bent 150 degrees geometry to one Cr(3) and one S(5) atom. In the eighteenth O site, O(18) is bonded in a bent 120 degrees geometry to one Cr(2) and one S(5) atom. In the nineteenth O site, O(19) is bonded in a bent 120 degrees geometry to one Cr(2) and one S(4,6) atom. In the twentieth O site, O(20) is bonded in a bent 150 degrees geometry to one Cr(1) and one S(4,6) atom. In the twenty-first O site, O(21) is bonded in a bent 150 degrees geometry to one Cr(2) and one S(2) atom. In the twenty-second O site, O(22) is bonded in a bent 150 degrees geometry to one Cr(3) and one S(4,6) atom. In the twenty-third O site, O(23) is bonded in a bent 150 degrees geometry to one Cr(2) and one S(3) atom. In the twenty-fourth O site, O(24) is bonded in a bent 150 degrees geometry to one Cr(2) and one S(1) atom.
MgCr3(SO4)6 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 3-coordinate geometry to one O(6), one O(7), and one O(9) atom. The Mg(1)-O(6) bond length is 1.97 Å. The Mg(1)-O(7) bond length is 1.97 Å. The Mg(1)-O(9) bond length is 1.97 Å. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(11), one O(12), one O(15), one O(20), one O(3), and one O(8) atom to form CrO6 octahedra that share  a cornercorner with one S(1)O4 tetrahedra;  a cornercorner with one S(2)O4 tetrahedra;  a cornercorner with one S(3)O4 tetrahedra;  a cornercorner with one S(5)O4 tetrahedra; and corners with two equivalent S(4,6)O4 tetrahedra. The Cr(1)-O(11) bond length is 1.99 Å. The Cr(1)-O(12) bond length is 1.99 Å. The Cr(1)-O(15) bond length is 2.03 Å. The Cr(1)-O(20) bond length is 1.99 Å. The Cr(1)-O(3) bond length is 2.03 Å. The Cr(1)-O(8) bond length is 2.03 Å. In the second Cr site, Cr(2) is bonded to one O(16), one O(18), one O(19), one O(21), one O(23), and one O(24) atom to form CrO6 octahedra that share  a cornercorner with one S(1)O4 tetrahedra;  a cornercorner with one S(2)O4 tetrahedra;  a cornercorner with one S(3)O4 tetrahedra;  a cornercorner with one S(5)O4 tetrahedra; and corners with two equivalent S(4,6)O4 tetrahedra. The Cr(2)-O(16) bond length is 2.04 Å. The Cr(2)-O(18) bond length is 2.04 Å. The Cr(2)-O(19) bond length is 2.04 Å. The Cr(2)-O(21) bond length is 2.04 Å. The Cr(2)-O(23) bond length is 2.04 Å. The Cr(2)-O(24) bond length is 2.04 Å. In the third Cr site, Cr(3) is bonded to one O(10), one O(13), one O(14), one O(17), one O(22), and one O(5) atom to form CrO6 octahedra that share  a cornercorner with one S(1)O4 tetrahedra;  a cornercorner with one S(2)O4 tetrahedra;  a cornercorner with one S(3)O4 tetrahedra;  a cornercorner with one S(5)O4 tetrahedra; and corners with two equivalent S(4,6)O4 tetrahedra. The Cr(3)-O(10) bond length is 1.96 Å. The Cr(3)-O(13) bond length is 1.95 Å. The Cr(3)-O(14) bond length is 1.95 Å. The Cr(3)-O(17) bond length is 1.96 Å. The Cr(3)-O(22) bond length is 1.96 Å. The Cr(3)-O(5) bond length is 1.95 Å. There are five inequivalent S sites. In the first S site, S(1) is bonded to one O(24), one O(3), one O(5), and one O(6) atom to form SO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra, and  a cornercorner with one Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-42°. The S(1)-O(24) bond length is 1.48 Å. The S(1)-O(3) bond length is 1.48 Å. The S(1)-O(5) bond length is 1.51 Å. The S(1)-O(6) bond length is 1.47 Å. In the second S site, S(2) is bonded to one O(13), one O(21), one O(7), and one O(8) atom to form SO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra, and  a cornercorner with one Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-42°. The S(2)-O(13) bond length is 1.51 Å. The S(2)-O(21) bond length is 1.48 Å. The S(2)-O(7) bond length is 1.47 Å. The S(2)-O(8) bond length is 1.48 Å. In the third S site, S(3) is bonded to one O(14), one O(15), one O(23), and one O(9) atom to form SO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra, and  a cornercorner with one Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-42°. The S(3)-O(14) bond length is 1.51 Å. The S(3)-O(15) bond length is 1.48 Å. The S(3)-O(23) bond length is 1.48 Å. The S(3)-O(9) bond length is 1.47 Å. In the fourth S site, S(4,6) is bonded to one O(10), one O(11), one O(16), and one O(2) atom to form SO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra, and  a cornercorner with one Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-53°. The S(4,6)-O(10) bond length is 1.50 Å. The S(4,6)-O(11) bond length is 1.50 Å. The S(4,6)-O(16) bond length is 1.52 Å. The S(4,6)-O(2) bond length is 1.43 Å. In the fifth S site, S(5) is bonded to one O(12), one O(17), one O(18), and one O(4) atom to form SO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra, and  a cornercorner with one Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-53°. The S(5)-O(12) bond length is 1.50 Å. The S(5)-O(17) bond length is 1.50 Å. The S(5)-O(18) bond length is 1.52 Å. The S(5)-O(4) bond length is 1.43 Å. There are twenty-four inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one S(4,6) atom. The O(1)-S(4,6) bond length is 1.43 Å. In the second O site, O(2) is bonded in a single-bond geometry to one S(4,6) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Cr(1) and one S(1) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one S(5) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Cr(3) and one S(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Mg(1) and one S(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Mg(1) and one S(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Cr(1) and one S(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Mg(1) and one S(3) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Cr(3) and one S(4,6) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Cr(1) and one S(4,6) atom. In the twelfth O site, O(12) is bonded in a bent 150 degrees geometry to one Cr(1) and one S(5) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Cr(3) and one S(2) atom. In the fourteenth O site, O(14) is bonded in a bent 150 degrees geometry to one Cr(3) and one S(3) atom. In the fifteenth O site, O(15) is bonded in a bent 150 degrees geometry to one Cr(1) and one S(3) atom. In the sixteenth O site, O(16) is bonded in a bent 120 degrees geometry to one Cr(2) and one S(4,6) atom. In the seventeenth O site, O(17) is bonded in a bent 150 degrees geometry to one Cr(3) and one S(5) atom. In the eighteenth O site, O(18) is bonded in a bent 120 degrees geometry to one Cr(2) and one S(5) atom. In the nineteenth O site, O(19) is bonded in a bent 120 degrees geometry to one Cr(2) and one S(4,6) atom. The O(19)-S(4,6) bond length is 1.52 Å. In the twentieth O site, O(20) is bonded in a bent 150 degrees geometry to one Cr(1) and one S(4,6) atom. The O(20)-S(4,6) bond length is 1.50 Å. In the twenty-first O site, O(21) is bonded in a bent 150 degrees geometry to one Cr(2) and one S(2) atom. In the twenty-second O site, O(22) is bonded in a bent 150 degrees geometry to one Cr(3) and one S(4,6) atom. The O(22)-S(4,6) bond length is 1.50 Å. In the twenty-third O site, O(23) is bonded in a bent 150 degrees geometry to one Cr(2) and one S(3) atom. In the twenty-fourth O site, O(24) is bonded in a bent 150 degrees geometry to one Cr(2) and one S(1) atom.