Mg(InSe2)2 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to one Se(3), two equivalent Se(1), and three equivalent Se(2) atoms to form distorted MgSe6 pentagonal pyramids that share corners with four equivalent In(1)Se6 octahedra, corners with two equivalent Mg(1)Se6 pentagonal pyramids, corners with two equivalent In(2)Se6 pentagonal pyramids, edges with two equivalent In(1)Se6 octahedra, edges with two equivalent Mg(1)Se6 pentagonal pyramids, and faces with two equivalent In(2)Se6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 30-48°. There are two inequivalent In sites. In the first In site, In(1) is bonded to one Se(2), one Se(3), and four equivalent Se(1) atoms to form distorted InSe6 octahedra that share corners with two equivalent In(2)Se6 pentagonal pyramids, corners with four equivalent Mg(1)Se6 pentagonal pyramids, edges with two equivalent In(1)Se6 octahedra, edges with two equivalent Mg(1)Se6 pentagonal pyramids, and faces with two equivalent In(2)Se6 pentagonal pyramids. In the second In site, In(2) is bonded to one Se(2), two equivalent Se(1), and three equivalent Se(3) atoms to form distorted InSe6 pentagonal pyramids that share corners with two equivalent In(1)Se6 octahedra, corners with two equivalent Mg(1)Se6 pentagonal pyramids, corners with two equivalent In(2)Se6 pentagonal pyramids, edges with two equivalent In(2)Se6 pentagonal pyramids, faces with two equivalent In(1)Se6 octahedra, and faces with two equivalent Mg(1)Se6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 68°. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a 4-coordinate geometry to one Mg(1), one In(2), and two equivalent In(1) atoms. In the second Se site, Se(2) is bonded to three equivalent Mg(1), one In(1), and one In(2) atom to form distorted SeMg3In2 square pyramids that share corners with two equivalent Se(2)Mg3In2 square pyramids, corners with three equivalent Se(3)MgIn4 trigonal bipyramids, edges with two equivalent Se(2)Mg3In2 square pyramids, and edges with two equivalent Se(3)MgIn4 trigonal bipyramids. In the third Se site, Se(3) is bonded to one Mg(1), one In(1), and three equivalent In(2) atoms to form distorted SeMgIn4 trigonal bipyramids that share corners with three equivalent Se(2)Mg3In2 square pyramids, corners with two equivalent Se(3)MgIn4 trigonal bipyramids, edges with two equivalent Se(2)Mg3In2 square pyramids, and edges with two equivalent Se(3)MgIn4 trigonal bipyramids.
Mg(InSe2)2 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to one Se(3), two equivalent Se(1), and three equivalent Se(2) atoms to form distorted MgSe6 pentagonal pyramids that share corners with four equivalent In(1)Se6 octahedra, corners with two equivalent Mg(1)Se6 pentagonal pyramids, corners with two equivalent In(2)Se6 pentagonal pyramids, edges with two equivalent In(1)Se6 octahedra, edges with two equivalent Mg(1)Se6 pentagonal pyramids, and faces with two equivalent In(2)Se6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 30-48°. The Mg(1)-Se(3) bond length is 2.59 Å. Both Mg(1)-Se(1) bond lengths are 2.93 Å. There is one shorter (2.67 Å) and two longer (2.99 Å) Mg(1)-Se(2) bond lengths. There are two inequivalent In sites. In the first In site, In(1) is bonded to one Se(2), one Se(3), and four equivalent Se(1) atoms to form distorted InSe6 octahedra that share corners with two equivalent In(2)Se6 pentagonal pyramids, corners with four equivalent Mg(1)Se6 pentagonal pyramids, edges with two equivalent In(1)Se6 octahedra, edges with two equivalent Mg(1)Se6 pentagonal pyramids, and faces with two equivalent In(2)Se6 pentagonal pyramids. The In(1)-Se(2) bond length is 2.71 Å. The In(1)-Se(3) bond length is 2.76 Å. There are two shorter (2.86 Å) and two longer (2.99 Å) In(1)-Se(1) bond lengths. In the second In site, In(2) is bonded to one Se(2), two equivalent Se(1), and three equivalent Se(3) atoms to form distorted InSe6 pentagonal pyramids that share corners with two equivalent In(1)Se6 octahedra, corners with two equivalent Mg(1)Se6 pentagonal pyramids, corners with two equivalent In(2)Se6 pentagonal pyramids, edges with two equivalent In(2)Se6 pentagonal pyramids, faces with two equivalent In(1)Se6 octahedra, and faces with two equivalent Mg(1)Se6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 68°. The In(2)-Se(2) bond length is 2.83 Å. Both In(2)-Se(1) bond lengths are 2.91 Å. There is one shorter (2.80 Å) and two longer (3.10 Å) In(2)-Se(3) bond lengths. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a 4-coordinate geometry to one Mg(1), one In(2), and two equivalent In(1) atoms. In the second Se site, Se(2) is bonded to three equivalent Mg(1), one In(1), and one In(2) atom to form distorted SeMg3In2 square pyramids that share corners with two equivalent Se(2)Mg3In2 square pyramids, corners with three equivalent Se(3)MgIn4 trigonal bipyramids, edges with two equivalent Se(2)Mg3In2 square pyramids, and edges with two equivalent Se(3)MgIn4 trigonal bipyramids. In the third Se site, Se(3) is bonded to one Mg(1), one In(1), and three equivalent In(2) atoms to form distorted SeMgIn4 trigonal bipyramids that share corners with three equivalent Se(2)Mg3In2 square pyramids, corners with two equivalent Se(3)MgIn4 trigonal bipyramids, edges with two equivalent Se(2)Mg3In2 square pyramids, and edges with two equivalent Se(3)MgIn4 trigonal bipyramids.