Mg(PtO2)3 crystallizes in the orthorhombic Cmmm space group. Mg(1) is bonded in a body-centered cubic geometry to four equivalent O(1) and four equivalent O(2) atoms. There are two inequivalent Pt sites. In the first Pt site, Pt(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form a mixture of distorted corner and edge-sharing PtO6 octahedra. The corner-sharing octahedral tilt angles are 59°. In the second Pt site, Pt(2) is bonded in a square co-planar geometry to four equivalent O(1) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Pt(2), and two equivalent Pt(1) atoms to form OMgPt3 tetrahedra that share corners with four equivalent O(2)Mg2Pt2 tetrahedra, corners with eight equivalent O(1)MgPt3 tetrahedra, edges with two equivalent O(2)Mg2Pt2 tetrahedra, and edges with two equivalent O(1)MgPt3 tetrahedra. In the second O site, O(2) is bonded to two equivalent Mg(1) and two equivalent Pt(1) atoms to form OMg2Pt2 tetrahedra that share corners with six equivalent O(2)Mg2Pt2 tetrahedra, corners with eight equivalent O(1)MgPt3 tetrahedra,  an edgeedge with one O(2)Mg2Pt2 tetrahedra, and edges with four equivalent O(1)MgPt3 tetrahedra.
Mg(PtO2)3 crystallizes in the orthorhombic Cmmm space group. Mg(1) is bonded in a body-centered cubic geometry to four equivalent O(1) and four equivalent O(2) atoms. All Mg(1)-O(1) bond lengths are 2.40 Å. All Mg(1)-O(2) bond lengths are 2.17 Å. There are two inequivalent Pt sites. In the first Pt site, Pt(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form a mixture of distorted corner and edge-sharing PtO6 octahedra. The corner-sharing octahedral tilt angles are 59°. Both Pt(1)-O(2) bond lengths are 2.05 Å. All Pt(1)-O(1) bond lengths are 2.03 Å. In the second Pt site, Pt(2) is bonded in a square co-planar geometry to four equivalent O(1) atoms. All Pt(2)-O(1) bond lengths are 1.97 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Pt(2), and two equivalent Pt(1) atoms to form OMgPt3 tetrahedra that share corners with four equivalent O(2)Mg2Pt2 tetrahedra, corners with eight equivalent O(1)MgPt3 tetrahedra, edges with two equivalent O(2)Mg2Pt2 tetrahedra, and edges with two equivalent O(1)MgPt3 tetrahedra. In the second O site, O(2) is bonded to two equivalent Mg(1) and two equivalent Pt(1) atoms to form OMg2Pt2 tetrahedra that share corners with six equivalent O(2)Mg2Pt2 tetrahedra, corners with eight equivalent O(1)MgPt3 tetrahedra,  an edgeedge with one O(2)Mg2Pt2 tetrahedra, and edges with four equivalent O(1)MgPt3 tetrahedra.