MgFe4As2O11 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(10), one O(3), one O(5), one O(6), and one O(8) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Fe(4)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra,  a cornercorner with one As(2)O4 tetrahedra,  a cornercorner with one Fe(2)O5 trigonal bipyramid,  a cornercorner with one Fe(3)O5 trigonal bipyramid,  an edgeedge with one As(2)O4 tetrahedra, and  an edgeedge with one Fe(3)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 70°. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 5-coordinate geometry to one O(1), one O(10), one O(2), one O(3), and one O(7) atom. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(9) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one As(1)O4 tetrahedra,  a cornercorner with one As(2)O4 tetrahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid,  a cornercorner with one Fe(3)O5 trigonal bipyramid, and edges with two equivalent Fe(4)O6 octahedra. In the third Fe site, Fe(3) is bonded to one O(10), one O(11), one O(2), one O(5), and one O(8) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one Fe(4)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid,  a cornercorner with one Fe(2)O5 trigonal bipyramid, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 66°. 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 corners with two equivalent As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid,  a cornercorner with one Fe(3)O5 trigonal bipyramid, and edges with two equivalent Fe(2)O5 trigonal bipyramids. 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 corners with two equivalent Fe(4)O6 octahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid,  a cornercorner with one Fe(2)O5 trigonal bipyramid, and corners with two equivalent Fe(3)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 45-53°. 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 corners with two equivalent Fe(4)O6 octahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid,  a cornercorner with one Fe(2)O5 trigonal bipyramid, corners with two equivalent Fe(3)O5 trigonal bipyramids, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 50-54°. There are eleven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Fe(1), one Fe(2), and one Fe(4) atom. In the second O site, O(2) is bonded in a trigonal pyramidal geometry to one Fe(1), one Fe(2), one Fe(3), and one Fe(4) atom. In the third O site, O(3) is bonded in a trigonal planar 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 trigonal planar geometry to one Mg(1), one Fe(3), and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Fe(4), and one As(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(4), and one As(1) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(3), and one As(2) atom. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one Fe(2), one Fe(4), and one As(1) atom. In the tenth O site, O(10) is bonded in a 4-coordinate 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 to one O(10), one O(3), one O(5), one O(6), and one O(8) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Fe(4)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra,  a cornercorner with one As(2)O4 tetrahedra,  a cornercorner with one Fe(2)O5 trigonal bipyramid,  a cornercorner with one Fe(3)O5 trigonal bipyramid,  an edgeedge with one As(2)O4 tetrahedra, and  an edgeedge with one Fe(3)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 70°. The Mg(1)-O(10) bond length is 2.17 Å. The Mg(1)-O(3) bond length is 1.93 Å. The Mg(1)-O(5) bond length is 2.10 Å. The Mg(1)-O(6) bond length is 2.06 Å. The Mg(1)-O(8) bond length is 2.23 Å. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 5-coordinate geometry to one O(1), one O(10), one O(2), one O(3), and one O(7) atom. The Fe(1)-O(1) bond length is 2.09 Å. The Fe(1)-O(10) bond length is 2.46 Å. The Fe(1)-O(2) bond length is 2.19 Å. The Fe(1)-O(3) bond length is 1.98 Å. The Fe(1)-O(7) bond length is 2.17 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(9) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one As(1)O4 tetrahedra,  a cornercorner with one As(2)O4 tetrahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid,  a cornercorner with one Fe(3)O5 trigonal bipyramid, and edges with two equivalent Fe(4)O6 octahedra. The Fe(2)-O(1) bond length is 1.95 Å. The Fe(2)-O(2) bond length is 2.01 Å. The Fe(2)-O(3) bond length is 1.87 Å. The Fe(2)-O(4) bond length is 2.02 Å. The Fe(2)-O(9) bond length is 2.17 Å. In the third Fe site, Fe(3) is bonded to one O(10), one O(11), one O(2), one O(5), and one O(8) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one Fe(4)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid,  a cornercorner with one Fe(2)O5 trigonal bipyramid, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 66°. The Fe(3)-O(10) bond length is 2.16 Å. The Fe(3)-O(11) bond length is 2.11 Å. The Fe(3)-O(2) bond length is 2.06 Å. The Fe(3)-O(5) bond length is 2.13 Å. The Fe(3)-O(8) bond length is 2.08 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 corners with two equivalent As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid,  a cornercorner with one Fe(3)O5 trigonal bipyramid, and edges with two equivalent Fe(2)O5 trigonal bipyramids. The Fe(4)-O(1) bond length is 1.91 Å. The Fe(4)-O(2) bond length is 1.98 Å. The Fe(4)-O(4) bond length is 2.26 Å. The Fe(4)-O(6) bond length is 2.20 Å. The Fe(4)-O(7) bond length is 2.03 Å. The Fe(4)-O(9) bond length is 2.06 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 corners with two equivalent Fe(4)O6 octahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid,  a cornercorner with one Fe(2)O5 trigonal bipyramid, and corners with two equivalent Fe(3)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 45-53°. The As(1)-O(11) bond length is 1.69 Å. The As(1)-O(5) bond length is 1.73 Å. The As(1)-O(7) bond length is 1.74 Å. The As(1)-O(9) bond length is 1.75 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 corners with two equivalent Fe(4)O6 octahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid,  a cornercorner with one Fe(2)O5 trigonal bipyramid, corners with two equivalent Fe(3)O5 trigonal bipyramids, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 50-54°. The As(2)-O(10) bond length is 1.74 Å. The As(2)-O(4) bond length is 1.75 Å. The As(2)-O(6) bond length is 1.72 Å. The As(2)-O(8) bond length is 1.71 Å. There are eleven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Fe(1), one Fe(2), and one Fe(4) atom. In the second O site, O(2) is bonded in a trigonal pyramidal geometry to one Fe(1), one Fe(2), one Fe(3), and one Fe(4) atom. In the third O site, O(3) is bonded in a trigonal planar 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 trigonal planar geometry to one Mg(1), one Fe(3), and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Fe(4), and one As(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(4), and one As(1) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(3), and one As(2) atom. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one Fe(2), one Fe(4), and one As(1) atom. In the tenth O site, O(10) is bonded in a 4-coordinate 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.