CaB2(H2O3)2 crystallizes in the monoclinic C2/c space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(3) atoms. B(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form corner-sharing BO4 tetrahedra. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(2) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(3) atom. There are three inequivalent O sites. In the first O site, O(2) is bonded in a distorted water-like geometry to one Ca(1), one B(1), and one H(1) atom. In the second O site, O(3) is bonded in a 2-coordinate geometry to two equivalent Ca(1), one B(1), and one H(2) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to one Ca(1) and two equivalent B(1) atoms.
CaB2(H2O3)2 crystallizes in the monoclinic C2/c space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(3) atoms. Both Ca(1)-O(1) bond lengths are 2.37 Å. Both Ca(1)-O(2) bond lengths are 2.51 Å. There are two shorter (2.45 Å) and two longer (2.85 Å) Ca(1)-O(3) bond lengths. B(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form corner-sharing BO4 tetrahedra. The B(1)-O(2) bond length is 1.52 Å. The B(1)-O(3) bond length is 1.50 Å. There is one shorter (1.46 Å) and one longer (1.47 Å) B(1)-O(1) bond length. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(2) atom. The H(1)-O(2) bond length is 0.99 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(3) atom. The H(2)-O(3) bond length is 0.98 Å. There are three inequivalent O sites. In the first O site, O(2) is bonded in a distorted water-like geometry to one Ca(1), one B(1), and one H(1) atom. In the second O site, O(3) is bonded in a 2-coordinate geometry to two equivalent Ca(1), one B(1), and one H(2) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to one Ca(1) and two equivalent B(1) atoms.