MgFe4As2O11 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 5-coordinate geometry to one O(10), one O(2), one O(3), one O(8), and one O(9) atom. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(10), one O(2), one O(3), one O(5), and one O(7) atom to form distorted FeO6 octahedra that share  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Fe(4)O6 octahedra,  a cornercorner with one As(2)O4 tetrahedra, corners with two equivalent As(1)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra,  an edgeedge with one Fe(4)O6 octahedra, and edges with two equivalent Fe(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-34°. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(8), and one O(9) atom to form distorted FeO6 octahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra,  an edgeedge with one Fe(3)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-23°. In the third Fe site, Fe(3) is bonded to one O(1), one O(10), one O(11), one O(2), one O(5), and one O(8) atom to form FeO6 octahedra that share  a cornercorner with one Fe(2)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra,  an edgeedge with one Fe(4)O6 octahedra, and edges with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 23°. In the fourth Fe site, Fe(4) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(9) atom to form FeO6 octahedra that share  a cornercorner with one Fe(1)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra,  an edgeedge with one Fe(3)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles are 34°. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(11), one O(5), one O(7), and one O(9) atom to form AsO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra, corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(3)O6 octahedra, and corners with two equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-57°. In the second As site, As(2) is bonded to one O(10), one O(4), one O(6), and one O(8) atom to form AsO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent Fe(3)O6 octahedra, and corners with two equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-63°. There are eleven inequivalent O sites. In the first O site, O(1) is bonded to one Fe(1), one Fe(2), one Fe(3), and one Fe(4) atom to form edge-sharing OFe4 tetrahedra. In the second O site, O(2) is bonded to one Mg(1), one Fe(1), one Fe(2), one Fe(3), and one Fe(4) atom to form distorted edge-sharing OMgFe4 square pyramids. In the third O site, O(3) is bonded in a T-shaped geometry to one Mg(1), one Fe(1), and one Fe(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Fe(2), one Fe(4), and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Fe(1), one Fe(3), and one As(1) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Fe(4) and one As(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(4), and one As(1) atom. In the eighth O site, O(8) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(2), one Fe(3), and one As(2) atom. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(2), one Fe(4), and one As(1) atom. In the tenth O site, O(10) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Fe(1), one Fe(3), and one As(2) atom. In the eleventh O site, O(11) is bonded in a bent 120 degrees geometry to one Fe(3) and one As(1) atom.
MgFe4As2O11 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 5-coordinate geometry to one O(10), one O(2), one O(3), one O(8), and one O(9) atom. The Mg(1)-O(10) bond length is 2.28 Å. The Mg(1)-O(2) bond length is 2.06 Å. The Mg(1)-O(3) bond length is 1.93 Å. The Mg(1)-O(8) bond length is 2.11 Å. The Mg(1)-O(9) bond length is 2.02 Å. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(10), one O(2), one O(3), one O(5), and one O(7) atom to form distorted FeO6 octahedra that share  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Fe(4)O6 octahedra,  a cornercorner with one As(2)O4 tetrahedra, corners with two equivalent As(1)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra,  an edgeedge with one Fe(4)O6 octahedra, and edges with two equivalent Fe(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-34°. The Fe(1)-O(1) bond length is 2.19 Å. The Fe(1)-O(10) bond length is 2.42 Å. The Fe(1)-O(2) bond length is 2.21 Å. The Fe(1)-O(3) bond length is 2.02 Å. The Fe(1)-O(5) bond length is 2.21 Å. The Fe(1)-O(7) bond length is 2.41 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(8), and one O(9) atom to form distorted FeO6 octahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra,  an edgeedge with one Fe(3)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-23°. The Fe(2)-O(1) bond length is 1.99 Å. The Fe(2)-O(2) bond length is 2.10 Å. The Fe(2)-O(3) bond length is 1.86 Å. The Fe(2)-O(4) bond length is 2.19 Å. The Fe(2)-O(8) bond length is 2.34 Å. The Fe(2)-O(9) bond length is 2.21 Å. In the third Fe site, Fe(3) is bonded to one O(1), one O(10), one O(11), one O(2), one O(5), and one O(8) atom to form FeO6 octahedra that share  a cornercorner with one Fe(2)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra,  an edgeedge with one Fe(4)O6 octahedra, and edges with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 23°. The Fe(3)-O(1) bond length is 2.11 Å. The Fe(3)-O(10) bond length is 2.17 Å. The Fe(3)-O(11) bond length is 2.00 Å. The Fe(3)-O(2) bond length is 2.39 Å. The Fe(3)-O(5) bond length is 2.17 Å. The Fe(3)-O(8) bond length is 2.21 Å. In the fourth Fe site, Fe(4) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(9) atom to form FeO6 octahedra that share  a cornercorner with one Fe(1)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra,  an edgeedge with one Fe(3)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles are 34°. The Fe(4)-O(1) bond length is 1.98 Å. The Fe(4)-O(2) bond length is 2.07 Å. The Fe(4)-O(4) bond length is 2.21 Å. The Fe(4)-O(6) bond length is 1.97 Å. The Fe(4)-O(7) bond length is 1.98 Å. The Fe(4)-O(9) bond length is 2.22 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(11), one O(5), one O(7), and one O(9) atom to form AsO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra, corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(3)O6 octahedra, and corners with two equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-57°. The As(1)-O(11) bond length is 1.68 Å. The As(1)-O(5) bond length is 1.71 Å. The As(1)-O(7) bond length is 1.74 Å. The As(1)-O(9) bond length is 1.80 Å. In the second As site, As(2) is bonded to one O(10), one O(4), one O(6), and one O(8) atom to form AsO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent Fe(3)O6 octahedra, and corners with two equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-63°. The As(2)-O(10) bond length is 1.74 Å. The As(2)-O(4) bond length is 1.71 Å. The As(2)-O(6) bond length is 1.73 Å. The As(2)-O(8) bond length is 1.75 Å. There are eleven inequivalent O sites. In the first O site, O(1) is bonded to one Fe(1), one Fe(2), one Fe(3), and one Fe(4) atom to form edge-sharing OFe4 tetrahedra. In the second O site, O(2) is bonded to one Mg(1), one Fe(1), one Fe(2), one Fe(3), and one Fe(4) atom to form distorted edge-sharing OMgFe4 square pyramids. In the third O site, O(3) is bonded in a T-shaped geometry to one Mg(1), one Fe(1), and one Fe(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Fe(2), one Fe(4), and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Fe(1), one Fe(3), and one As(1) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Fe(4) and one As(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(4), and one As(1) atom. In the eighth O site, O(8) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(2), one Fe(3), and one As(2) atom. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(2), one Fe(4), and one As(1) atom. In the tenth O site, O(10) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Fe(1), one Fe(3), and one As(2) atom. In the eleventh O site, O(11) is bonded in a bent 120 degrees geometry to one Fe(3) and one As(1) atom.