UH2Se2O9 crystallizes in the monoclinic C2/c space group. U(1) is bonded to one O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms to form distorted UO7 pentagonal bipyramids that share corners with four equivalent Se(1)O4 tetrahedra. H(1) is bonded in a single-bond geometry to one O(1) atom. Se(1) is bonded to one O(2), one O(5), and two equivalent O(4) atoms to form distorted SeO4 tetrahedra that share corners with two equivalent U(1)O7 pentagonal bipyramids and corners with two equivalent Se(1)O4 tetrahedra. There are five inequivalent O sites. In the first O site, O(5) is bonded in a 2-coordinate geometry to one U(1) and one Se(1) atom. In the second O site, O(1) is bonded in a water-like geometry to one U(1) and two equivalent H(1) atoms. In the third O site, O(2) is bonded in a linear geometry to one U(1) and one Se(1) atom. In the fourth O site, O(3) is bonded in a single-bond geometry to one U(1) atom. In the fifth O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent Se(1) atoms.
UH2Se2O9 crystallizes in the monoclinic C2/c space group. U(1) is bonded to one O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms to form distorted UO7 pentagonal bipyramids that share corners with four equivalent Se(1)O4 tetrahedra. The U(1)-O(1) bond length is 2.45 Å. Both U(1)-O(2) bond lengths are 2.32 Å. Both U(1)-O(3) bond lengths are 1.80 Å. Both U(1)-O(5) bond lengths are 2.49 Å. H(1) is bonded in a single-bond geometry to one O(1) atom. The H(1)-O(1) bond length is 0.99 Å. Se(1) is bonded to one O(2), one O(5), and two equivalent O(4) atoms to form distorted SeO4 tetrahedra that share corners with two equivalent U(1)O7 pentagonal bipyramids and corners with two equivalent Se(1)O4 tetrahedra. The Se(1)-O(2) bond length is 1.69 Å. The Se(1)-O(5) bond length is 1.70 Å. There is one shorter (1.70 Å) and one longer (2.32 Å) Se(1)-O(4) bond length. There are five inequivalent O sites. In the first O site, O(5) is bonded in a 2-coordinate geometry to one U(1) and one Se(1) atom. In the second O site, O(1) is bonded in a water-like geometry to one U(1) and two equivalent H(1) atoms. In the third O site, O(2) is bonded in a linear geometry to one U(1) and one Se(1) atom. In the fourth O site, O(3) is bonded in a single-bond geometry to one U(1) atom. In the fifth O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent Se(1) atoms.