Na4H6Se2O11 crystallizes in the orthorhombic Fdd2 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(4), two equivalent O(3), and two equivalent O(5) atoms. In the second Na site, Na(2) is bonded to one O(1), one O(4), one O(6), and two equivalent O(2) atoms to form distorted NaO5 trigonal bipyramids that share corners with four equivalent Se(1)O4 tetrahedra and corners with three equivalent Na(2)O5 trigonal bipyramids. There are three inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(5) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(5) atom. In the third H site, H(3) is bonded in a distorted single-bond geometry to one O(1) and one O(6) atom. Se(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SeO4 tetrahedra that share corners with four equivalent Na(2)O5 trigonal bipyramids. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one H(3), and one Se(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), two equivalent Na(2), and one Se(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to two equivalent Na(1) and one Se(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Na(2), and one Se(1) atom. In the fifth O site, O(5) is bonded in a distorted water-like geometry to two equivalent Na(1), one H(1), and one H(2) atom. In the sixth O site, O(6) is bonded in a distorted water-like geometry to two equivalent Na(2) and two equivalent H(3) atoms.
Na4H6Se2O11 crystallizes in the orthorhombic Fdd2 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(4), two equivalent O(3), and two equivalent O(5) atoms. The Na(1)-O(1) bond length is 2.48 Å. The Na(1)-O(2) bond length is 2.89 Å. The Na(1)-O(4) bond length is 2.79 Å. There is one shorter (2.44 Å) and one longer (2.52 Å) Na(1)-O(3) bond length. There is one shorter (2.42 Å) and one longer (2.51 Å) Na(1)-O(5) bond length. In the second Na site, Na(2) is bonded to one O(1), one O(4), one O(6), and two equivalent O(2) atoms to form distorted NaO5 trigonal bipyramids that share corners with four equivalent Se(1)O4 tetrahedra and corners with three equivalent Na(2)O5 trigonal bipyramids. The Na(2)-O(1) bond length is 2.47 Å. The Na(2)-O(4) bond length is 2.39 Å. The Na(2)-O(6) bond length is 2.40 Å. There is one shorter (2.35 Å) and one longer (2.38 Å) Na(2)-O(2) bond length. There are three inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(5) atom. The H(1)-O(5) bond length is 0.99 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(5) atom. The H(2)-O(5) bond length is 0.99 Å. In the third H site, H(3) is bonded in a distorted single-bond geometry to one O(1) and one O(6) atom. The H(3)-O(1) bond length is 1.71 Å. The H(3)-O(6) bond length is 1.00 Å. Se(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SeO4 tetrahedra that share corners with four equivalent Na(2)O5 trigonal bipyramids. The Se(1)-O(1) bond length is 1.69 Å. The Se(1)-O(2) bond length is 1.67 Å. The Se(1)-O(3) bond length is 1.67 Å. The Se(1)-O(4) bond length is 1.68 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one H(3), and one Se(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), two equivalent Na(2), and one Se(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to two equivalent Na(1) and one Se(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Na(2), and one Se(1) atom. In the fifth O site, O(5) is bonded in a distorted water-like geometry to two equivalent Na(1), one H(1), and one H(2) atom. In the sixth O site, O(6) is bonded in a distorted water-like geometry to two equivalent Na(2) and two equivalent H(3) atoms.