MgRe2NiO8 crystallizes in the trigonal P3 space group. Mg(1) is bonded to one O(1) and three equivalent O(4) atoms to form MgO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra,  a cornercorner with one Re(2)O4 tetrahedra, and corners with three equivalent Re(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 63°. There are two inequivalent Re sites. In the first Re site, Re(1) is bonded to one O(2) and three equivalent O(4) atoms to form ReO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra and corners with three equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 47°. In the second Re site, Re(2) is bonded to one O(1) and three equivalent O(3) atoms to form ReO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra and  a cornercorner with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 37°. Ni(1) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form NiO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Re(1)O4 tetrahedra, and corners with three equivalent Re(2)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Mg(1) and one Re(2) atom. In the second O site, O(2) is bonded in a single-bond geometry to one Re(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Re(2) and one Ni(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Mg(1), one Re(1), and one Ni(1) atom.
MgRe2NiO8 crystallizes in the trigonal P3 space group. Mg(1) is bonded to one O(1) and three equivalent O(4) atoms to form MgO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra,  a cornercorner with one Re(2)O4 tetrahedra, and corners with three equivalent Re(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 63°. The Mg(1)-O(1) bond length is 1.97 Å. All Mg(1)-O(4) bond lengths are 1.99 Å. There are two inequivalent Re sites. In the first Re site, Re(1) is bonded to one O(2) and three equivalent O(4) atoms to form ReO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra and corners with three equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 47°. The Re(1)-O(2) bond length is 1.72 Å. All Re(1)-O(4) bond lengths are 1.85 Å. In the second Re site, Re(2) is bonded to one O(1) and three equivalent O(3) atoms to form ReO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra and  a cornercorner with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 37°. The Re(2)-O(1) bond length is 1.79 Å. All Re(2)-O(3) bond lengths are 1.76 Å. Ni(1) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form NiO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Re(1)O4 tetrahedra, and corners with three equivalent Re(2)O4 tetrahedra. All Ni(1)-O(3) bond lengths are 2.10 Å. All Ni(1)-O(4) bond lengths are 2.09 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Mg(1) and one Re(2) atom. In the second O site, O(2) is bonded in a single-bond geometry to one Re(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Re(2) and one Ni(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Mg(1), one Re(1), and one Ni(1) atom.