Mn(HPO3) crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(6), and two equivalent O(4) atoms. In the second Mn site, Mn(2) is bonded to one O(1), one O(3), one O(5), one O(6), and two equivalent O(2) atoms to form distorted MnO6 octahedra that share corners with two equivalent P(2)HO3 tetrahedra, corners with four equivalent P(1)HO3 tetrahedra, and  an edgeedge with one Mn(2)O6 octahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one H(1), one O(1), one O(2), and one O(6) atom to form distorted PHO3 tetrahedra that share corners with four equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-58°. In the second P site, P(2) is bonded to one H(2), one O(3), one O(4), and one O(5) atom to form distorted PHO3 tetrahedra that share corners with two equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-45°. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one P(1) atom. In the second H site, H(2) is bonded in a single-bond geometry to one P(2) atom. There are six inequivalent O sites. In the first O site, O(3) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one P(2) atom. In the second O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Mn(1) and one P(2) atom. In the third O site, O(5) is bonded in a bent 150 degrees geometry to one Mn(2) and one P(2) atom. In the fourth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Mn(1), one Mn(2), and one P(1) atom. In the fifth O site, O(1) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one P(1) atom. In the sixth O site, O(2) is bonded in a 4-coordinate geometry to one Mn(1), two equivalent Mn(2), and one P(1) atom.
Mn(HPO3) crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(6), and two equivalent O(4) atoms. The Mn(1)-O(1) bond length is 2.24 Å. The Mn(1)-O(2) bond length is 2.73 Å. The Mn(1)-O(3) bond length is 2.14 Å. The Mn(1)-O(6) bond length is 2.17 Å. There is one shorter (2.11 Å) and one longer (2.23 Å) Mn(1)-O(4) bond length. In the second Mn site, Mn(2) is bonded to one O(1), one O(3), one O(5), one O(6), and two equivalent O(2) atoms to form distorted MnO6 octahedra that share corners with two equivalent P(2)HO3 tetrahedra, corners with four equivalent P(1)HO3 tetrahedra, and  an edgeedge with one Mn(2)O6 octahedra. The Mn(2)-O(1) bond length is 2.23 Å. The Mn(2)-O(3) bond length is 2.29 Å. The Mn(2)-O(5) bond length is 2.09 Å. The Mn(2)-O(6) bond length is 2.22 Å. There is one shorter (2.21 Å) and one longer (2.46 Å) Mn(2)-O(2) bond length. There are two inequivalent P sites. In the first P site, P(1) is bonded to one H(1), one O(1), one O(2), and one O(6) atom to form distorted PHO3 tetrahedra that share corners with four equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-58°. The P(1)-H(1) bond length is 1.41 Å. The P(1)-O(1) bond length is 1.55 Å. The P(1)-O(2) bond length is 1.56 Å. The P(1)-O(6) bond length is 1.55 Å. In the second P site, P(2) is bonded to one H(2), one O(3), one O(4), and one O(5) atom to form distorted PHO3 tetrahedra that share corners with two equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 36-45°. The P(2)-H(2) bond length is 1.41 Å. The P(2)-O(3) bond length is 1.55 Å. The P(2)-O(4) bond length is 1.56 Å. The P(2)-O(5) bond length is 1.52 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one P(1) atom. In the second H site, H(2) is bonded in a single-bond geometry to one P(2) atom. There are six inequivalent O sites. In the first O site, O(3) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one P(2) atom. In the second O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Mn(1) and one P(2) atom. In the third O site, O(5) is bonded in a bent 150 degrees geometry to one Mn(2) and one P(2) atom. In the fourth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Mn(1), one Mn(2), and one P(1) atom. In the fifth O site, O(1) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one P(1) atom. In the sixth O site, O(2) is bonded in a 4-coordinate geometry to one Mn(1), two equivalent Mn(2), and one P(1) atom.