MgFe4As2O11 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(11), one O(3), and one O(7) atom to form MgO4 trigonal pyramids that share corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent Fe(3)O6 octahedra, corners with two equivalent Fe(4)O6 octahedra, and corners with two equivalent As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-89°. 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(5) atom. 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(3)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra, corners with two equivalent Mg(1)O4 trigonal pyramids,  an edgeedge with one Fe(3)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles are 27°. 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, corners with two equivalent Mg(1)O4 trigonal pyramids,  an edgeedge with one Fe(2)O6 octahedra, and  an edgeedge with one Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles are 27°. 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, corners with two equivalent Mg(1)O4 trigonal pyramids,  an edgeedge with one Fe(3)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. 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(3)O6 octahedra, corners with two equivalent Fe(4)O6 octahedra, and corners with two equivalent Mg(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 43-60°. 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(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 46-57°. There are eleven inequivalent O sites. In the first O site, O(1) 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 trigonal bipyramids. In the second O site, O(2) is bonded to one Fe(1), one Fe(2), one Fe(3), and one Fe(4) atom to form distorted edge-sharing OFe4 tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one Fe(1), and one Fe(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate 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 Fe(1), one Fe(3), and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees 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 Mg(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 Fe(2), 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 distorted trigonal non-coplanar geometry to one Fe(1), one Fe(3), and one As(2) atom. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one Mg(1), one Fe(3), and one As(1) atom.
MgFe4As2O11 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(11), one O(3), and one O(7) atom to form MgO4 trigonal pyramids that share corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent Fe(3)O6 octahedra, corners with two equivalent Fe(4)O6 octahedra, and corners with two equivalent As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-89°. The Mg(1)-O(1) bond length is 2.02 Å. The Mg(1)-O(11) bond length is 1.97 Å. The Mg(1)-O(3) bond length is 2.00 Å. The Mg(1)-O(7) bond length is 2.05 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(5) atom. The Fe(1)-O(1) bond length is 2.36 Å. The Fe(1)-O(10) bond length is 2.10 Å. The Fe(1)-O(2) bond length is 2.18 Å. The Fe(1)-O(3) bond length is 2.02 Å. The Fe(1)-O(5) bond length is 2.08 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(3)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra, corners with two equivalent Mg(1)O4 trigonal pyramids,  an edgeedge with one Fe(3)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles are 27°. The Fe(2)-O(1) bond length is 2.13 Å. The Fe(2)-O(2) bond length is 2.07 Å. The Fe(2)-O(3) bond length is 1.86 Å. The Fe(2)-O(4) bond length is 2.28 Å. The Fe(2)-O(8) bond length is 2.17 Å. The Fe(2)-O(9) bond length is 2.22 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, corners with two equivalent Mg(1)O4 trigonal pyramids,  an edgeedge with one Fe(2)O6 octahedra, and  an edgeedge with one Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles are 27°. The Fe(3)-O(1) bond length is 1.98 Å. The Fe(3)-O(10) bond length is 2.07 Å. The Fe(3)-O(11) bond length is 2.07 Å. The Fe(3)-O(2) bond length is 1.97 Å. The Fe(3)-O(5) bond length is 2.26 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, corners with two equivalent Mg(1)O4 trigonal pyramids,  an edgeedge with one Fe(3)O6 octahedra, and edges with two equivalent Fe(2)O6 octahedra. The Fe(4)-O(1) bond length is 2.23 Å. The Fe(4)-O(2) bond length is 2.14 Å. The Fe(4)-O(4) bond length is 2.09 Å. The Fe(4)-O(6) bond length is 2.09 Å. The Fe(4)-O(7) bond length is 2.20 Å. The Fe(4)-O(9) bond length is 2.12 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(3)O6 octahedra, corners with two equivalent Fe(4)O6 octahedra, and corners with two equivalent Mg(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 43-60°. The As(1)-O(11) bond length is 1.74 Å. The As(1)-O(5) bond length is 1.72 Å. The As(1)-O(7) bond length is 1.72 Å. The As(1)-O(9) bond length is 1.72 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(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 46-57°. The As(2)-O(10) bond length is 1.73 Å. The As(2)-O(4) bond length is 1.73 Å. The As(2)-O(6) bond length is 1.70 Å. The As(2)-O(8) bond length is 1.76 Å. There are eleven inequivalent O sites. In the first O site, O(1) 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 trigonal bipyramids. In the second O site, O(2) is bonded to one Fe(1), one Fe(2), one Fe(3), and one Fe(4) atom to form distorted edge-sharing OFe4 tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one Fe(1), and one Fe(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate 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 Fe(1), one Fe(3), and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees 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 Mg(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 Fe(2), 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 distorted trigonal non-coplanar geometry to one Fe(1), one Fe(3), and one As(2) atom. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one Mg(1), one Fe(3), and one As(1) atom.