NaNi2H3(SO5)2 crystallizes in the monoclinic Cm space group. Na(1) is bonded to one O(2), two equivalent O(4), and two equivalent O(5) atoms to form distorted NaO5 trigonal bipyramids that share corners with two equivalent S(2)O4 tetrahedra and corners with two equivalent Ni(1)O5 trigonal bipyramids. Ni(1) is bonded to one O(1), one O(2), one O(3), one O(6), and one O(7) atom to form NiO5 trigonal bipyramids that share  a cornercorner with one S(2)O4 tetrahedra,  a cornercorner with one Na(1)O5 trigonal bipyramid,  an edgeedge with one Ni(1)O5 trigonal bipyramid, and  a faceface with one Ni(1)O5 trigonal bipyramid. There are three inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(3) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(2) atom. In the third H site, H(3) is bonded in a single-bond geometry to one O(6) atom. There are two inequivalent S sites. In the first S site, S(1) is bonded in a distorted trigonal non-coplanar geometry to one O(3) and two equivalent O(5) atoms. In the second S site, S(2) is bonded to one O(6), one O(8), and two equivalent O(4) atoms to form SO4 tetrahedra that share corners with two equivalent Na(1)O5 trigonal bipyramids and corners with two equivalent Ni(1)O5 trigonal bipyramids. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Ni(1) and one O(7) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Na(1), two equivalent Ni(1), and one H(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to two equivalent Ni(1), one H(1), and one S(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Na(1) and one S(2) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Na(1) and one S(1) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to two equivalent Ni(1), one H(3), and one S(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Ni(1) and one O(1) atom. In the eighth O site, O(8) is bonded in a single-bond geometry to one S(2) atom.
NaNi2H3(SO5)2 crystallizes in the monoclinic Cm space group. Na(1) is bonded to one O(2), two equivalent O(4), and two equivalent O(5) atoms to form distorted NaO5 trigonal bipyramids that share corners with two equivalent S(2)O4 tetrahedra and corners with two equivalent Ni(1)O5 trigonal bipyramids. The Na(1)-O(2) bond length is 2.57 Å. Both Na(1)-O(4) bond lengths are 2.37 Å. Both Na(1)-O(5) bond lengths are 2.41 Å. Ni(1) is bonded to one O(1), one O(2), one O(3), one O(6), and one O(7) atom to form NiO5 trigonal bipyramids that share  a cornercorner with one S(2)O4 tetrahedra,  a cornercorner with one Na(1)O5 trigonal bipyramid,  an edgeedge with one Ni(1)O5 trigonal bipyramid, and  a faceface with one Ni(1)O5 trigonal bipyramid. The Ni(1)-O(1) bond length is 1.97 Å. The Ni(1)-O(2) bond length is 1.94 Å. The Ni(1)-O(3) bond length is 2.08 Å. The Ni(1)-O(6) bond length is 2.21 Å. The Ni(1)-O(7) bond length is 1.98 Å. There are three inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(3) atom. The H(1)-O(3) bond length is 0.98 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(2) atom. The H(2)-O(2) bond length is 0.97 Å. In the third H site, H(3) is bonded in a single-bond geometry to one O(6) atom. The H(3)-O(6) bond length is 0.99 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded in a distorted trigonal non-coplanar geometry to one O(3) and two equivalent O(5) atoms. The S(1)-O(3) bond length is 2.04 Å. Both S(1)-O(5) bond lengths are 1.47 Å. In the second S site, S(2) is bonded to one O(6), one O(8), and two equivalent O(4) atoms to form SO4 tetrahedra that share corners with two equivalent Na(1)O5 trigonal bipyramids and corners with two equivalent Ni(1)O5 trigonal bipyramids. The S(2)-O(6) bond length is 1.76 Å. The S(2)-O(8) bond length is 1.44 Å. Both S(2)-O(4) bond lengths are 1.45 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Ni(1) and one O(7) atom. The O(1)-O(7) bond length is 1.51 Å. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Na(1), two equivalent Ni(1), and one H(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to two equivalent Ni(1), one H(1), and one S(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Na(1) and one S(2) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Na(1) and one S(1) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to two equivalent Ni(1), one H(3), and one S(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Ni(1) and one O(1) atom. In the eighth O site, O(8) is bonded in a single-bond geometry to one S(2) atom.