Na2Ni3(P2O7)2 crystallizes in the monoclinic P2_1/c space group. Na(1) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(5), one O(6), and one O(7) atom. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(6) atoms to form NiO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra and corners with four equivalent P(1)O4 tetrahedra. In the second Ni site, Ni(2) is bonded in a 5-coordinate geometry to one O(1), one O(5), one O(6), one O(7), and two equivalent O(2) atoms. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with two equivalent Ni(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 43-61°. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 58°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Ni(1), one Ni(2), and one P(1) atom to form distorted corner-sharing ONaNi2P trigonal pyramids. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Ni(2) and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Ni(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Ni(2), and one P(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Na(1), one Ni(1), one Ni(2), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Na(1), one Ni(2), and one P(2) atom.
Na2Ni3(P2O7)2 crystallizes in the monoclinic P2_1/c space group. Na(1) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(5), one O(6), and one O(7) atom. The Na(1)-O(1) bond length is 2.39 Å. The Na(1)-O(3) bond length is 2.21 Å. The Na(1)-O(5) bond length is 2.24 Å. The Na(1)-O(6) bond length is 2.48 Å. The Na(1)-O(7) bond length is 2.23 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(6) atoms to form NiO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra and corners with four equivalent P(1)O4 tetrahedra. Both Ni(1)-O(1) bond lengths are 2.12 Å. Both Ni(1)-O(3) bond lengths are 2.09 Å. Both Ni(1)-O(6) bond lengths are 2.14 Å. In the second Ni site, Ni(2) is bonded in a 5-coordinate geometry to one O(1), one O(5), one O(6), one O(7), and two equivalent O(2) atoms. The Ni(2)-O(1) bond length is 2.09 Å. The Ni(2)-O(5) bond length is 2.02 Å. The Ni(2)-O(6) bond length is 2.56 Å. The Ni(2)-O(7) bond length is 2.08 Å. There is one shorter (2.07 Å) and one longer (2.09 Å) Ni(2)-O(2) bond length. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with two equivalent Ni(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 43-61°. The P(1)-O(1) bond length is 1.55 Å. The P(1)-O(2) bond length is 1.55 Å. The P(1)-O(3) bond length is 1.51 Å. The P(1)-O(4) bond length is 1.60 Å. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 58°. The P(2)-O(4) bond length is 1.63 Å. The P(2)-O(5) bond length is 1.52 Å. The P(2)-O(6) bond length is 1.55 Å. The P(2)-O(7) bond length is 1.52 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Ni(1), one Ni(2), and one P(1) atom to form distorted corner-sharing ONaNi2P trigonal pyramids. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Ni(2) and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Ni(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Ni(2), and one P(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Na(1), one Ni(1), one Ni(2), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Na(1), one Ni(2), and one P(2) atom.