MgNiF5 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded in a 7-coordinate geometry to one F(3), one F(4), one F(5), two equivalent F(1), and two equivalent F(2) atoms. Ni(1) is bonded to one F(1), one F(2), one F(3), one F(4), and two equivalent F(5) atoms to form corner-sharing NiF6 octahedra. The corner-sharing octahedral tilt angles are 45°. There are five inequivalent F sites. In the first F site, F(1) is bonded in a 3-coordinate geometry to two equivalent Mg(1) and one Ni(1) atom. In the second F site, F(2) is bonded in a 3-coordinate geometry to two equivalent Mg(1) and one Ni(1) atom. In the third F site, F(3) is bonded in a bent 150 degrees geometry to one Mg(1) and one Ni(1) atom. In the fourth F site, F(4) is bonded in a linear geometry to one Mg(1) and one Ni(1) atom. In the fifth F site, F(5) is bonded in a trigonal planar geometry to one Mg(1) and two equivalent Ni(1) atoms.
MgNiF5 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded in a 7-coordinate geometry to one F(3), one F(4), one F(5), two equivalent F(1), and two equivalent F(2) atoms. The Mg(1)-F(3) bond length is 1.98 Å. The Mg(1)-F(4) bond length is 1.97 Å. The Mg(1)-F(5) bond length is 2.11 Å. There is one shorter (2.03 Å) and one longer (2.48 Å) Mg(1)-F(1) bond length. There is one shorter (2.03 Å) and one longer (2.36 Å) Mg(1)-F(2) bond length. Ni(1) is bonded to one F(1), one F(2), one F(3), one F(4), and two equivalent F(5) atoms to form corner-sharing NiF6 octahedra. The corner-sharing octahedral tilt angles are 45°. The Ni(1)-F(1) bond length is 1.93 Å. The Ni(1)-F(2) bond length is 1.87 Å. The Ni(1)-F(3) bond length is 1.84 Å. The Ni(1)-F(4) bond length is 1.87 Å. Both Ni(1)-F(5) bond lengths are 1.99 Å. There are five inequivalent F sites. In the first F site, F(1) is bonded in a 3-coordinate geometry to two equivalent Mg(1) and one Ni(1) atom. In the second F site, F(2) is bonded in a 3-coordinate geometry to two equivalent Mg(1) and one Ni(1) atom. In the third F site, F(3) is bonded in a bent 150 degrees geometry to one Mg(1) and one Ni(1) atom. In the fourth F site, F(4) is bonded in a linear geometry to one Mg(1) and one Ni(1) atom. In the fifth F site, F(5) is bonded in a trigonal planar geometry to one Mg(1) and two equivalent Ni(1) atoms.