SrMg(NiO2)4 crystallizes in the monoclinic C2/m space group. Sr(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form distorted SrO6 octahedra that share corners with six equivalent Ni(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with four equivalent Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-20°. Mg(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form distorted MgO6 octahedra that share corners with six equivalent Ni(2)O6 octahedra, edges with two equivalent Sr(1)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with four equivalent Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 16-17°. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent Sr(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with four equivalent Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-20°. In the second Ni site, Ni(2) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Sr(1)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with four equivalent Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 16-17°. In the third Ni site, Ni(3) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NiO6 octahedra that share edges with two equivalent Sr(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(3)O6 octahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted see-saw-like geometry to one Sr(1), one Ni(1), and two equivalent Ni(3) atoms. In the second O site, O(2) is bonded to one Sr(1), one Mg(1), one Ni(1), one Ni(2), and one Ni(3) atom to form a mixture of corner and edge-sharing OSrMgNi3 square pyramids. In the third O site, O(3) is bonded in a see-saw-like geometry to one Mg(1), one Ni(2), and two equivalent Ni(3) atoms.
SrMg(NiO2)4 crystallizes in the monoclinic C2/m space group. Sr(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form distorted SrO6 octahedra that share corners with six equivalent Ni(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with four equivalent Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-20°. Both Sr(1)-O(1) bond lengths are 2.38 Å. All Sr(1)-O(2) bond lengths are 2.35 Å. Mg(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form distorted MgO6 octahedra that share corners with six equivalent Ni(2)O6 octahedra, edges with two equivalent Sr(1)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with four equivalent Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 16-17°. Both Mg(1)-O(3) bond lengths are 2.29 Å. All Mg(1)-O(2) bond lengths are 2.24 Å. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent Sr(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with four equivalent Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-20°. Both Ni(1)-O(1) bond lengths are 2.02 Å. All Ni(1)-O(2) bond lengths are 2.04 Å. In the second Ni site, Ni(2) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Sr(1)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with four equivalent Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 16-17°. Both Ni(2)-O(3) bond lengths are 2.09 Å. All Ni(2)-O(2) bond lengths are 2.17 Å. In the third Ni site, Ni(3) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NiO6 octahedra that share edges with two equivalent Sr(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(3)O6 octahedra. Both Ni(3)-O(1) bond lengths are 1.92 Å. Both Ni(3)-O(2) bond lengths are 1.90 Å. Both Ni(3)-O(3) bond lengths are 1.96 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted see-saw-like geometry to one Sr(1), one Ni(1), and two equivalent Ni(3) atoms. In the second O site, O(2) is bonded to one Sr(1), one Mg(1), one Ni(1), one Ni(2), and one Ni(3) atom to form a mixture of corner and edge-sharing OSrMgNi3 square pyramids. In the third O site, O(3) is bonded in a see-saw-like geometry to one Mg(1), one Ni(2), and two equivalent Ni(3) atoms.