Na2As4O11 crystallizes in the monoclinic C2/c space group. Na(1) is bonded in a 7-coordinate geometry to one O(2), two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing AsO4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-59°. In the second As site, As(2) is bonded to one O(2), one O(3), one O(4), one O(6), and two equivalent O(5) atoms to form AsO6 octahedra that share  a cornercorner with one As(2)O6 octahedra, corners with three equivalent As(1)O4 tetrahedra, and  an edgeedge with one As(2)O6 octahedra. The corner-sharing octahedral tilt angles are 45°. There are six inequivalent O sites. In the first O site, O(3) is bonded in a bent 120 degrees geometry to one As(1) and one As(2) atom. In the second O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent Na(1), one As(1), and one As(2) atom. In the third O site, O(5) is bonded to two equivalent Na(1) and two equivalent As(2) atoms to form distorted edge-sharing ONa2As2 trigonal pyramids. In the fourth O site, O(6) is bonded in a distorted bent 150 degrees geometry to two equivalent As(2) atoms. In the fifth O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Na(1) and one As(1) atom. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one As(1), and one As(2) atom.
Na2As4O11 crystallizes in the monoclinic C2/c space group. Na(1) is bonded in a 7-coordinate geometry to one O(2), two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms. The Na(1)-O(2) bond length is 2.54 Å. There is one shorter (2.25 Å) and one longer (2.35 Å) Na(1)-O(1) bond length. There is one shorter (2.72 Å) and one longer (2.95 Å) Na(1)-O(4) bond length. There is one shorter (2.48 Å) and one longer (2.53 Å) Na(1)-O(5) bond length. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing AsO4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-59°. The As(1)-O(1) bond length is 1.64 Å. The As(1)-O(2) bond length is 1.71 Å. The As(1)-O(3) bond length is 1.72 Å. The As(1)-O(4) bond length is 1.74 Å. In the second As site, As(2) is bonded to one O(2), one O(3), one O(4), one O(6), and two equivalent O(5) atoms to form AsO6 octahedra that share  a cornercorner with one As(2)O6 octahedra, corners with three equivalent As(1)O4 tetrahedra, and  an edgeedge with one As(2)O6 octahedra. The corner-sharing octahedral tilt angles are 45°. The As(2)-O(2) bond length is 1.86 Å. The As(2)-O(3) bond length is 1.83 Å. The As(2)-O(4) bond length is 1.86 Å. The As(2)-O(6) bond length is 1.79 Å. Both As(2)-O(5) bond lengths are 1.83 Å. There are six inequivalent O sites. In the first O site, O(3) is bonded in a bent 120 degrees geometry to one As(1) and one As(2) atom. In the second O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent Na(1), one As(1), and one As(2) atom. In the third O site, O(5) is bonded to two equivalent Na(1) and two equivalent As(2) atoms to form distorted edge-sharing ONa2As2 trigonal pyramids. In the fourth O site, O(6) is bonded in a distorted bent 150 degrees geometry to two equivalent As(2) atoms. In the fifth O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Na(1) and one As(1) atom. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one As(1), and one As(2) atom.