CaSn3(P2O7)2 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 3-coordinate geometry to one O(3), one O(5), and one O(7) atom. In the second Sn site, Sn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms to form distorted SnO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra and corners with four equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Sn(2)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 55°. In the second P site, P(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Sn(2)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 53-63°. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a 2-coordinate geometry to one Ca(1), one Sn(1), and one P(1) atom. In the second O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Sn(2) and one P(2) atom. In the third O site, O(7) is bonded in a 2-coordinate geometry to one Sn(1) and one P(2) atom. In the fourth O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(2), and one P(2) atom. In the fifth O site, O(2) is bonded in a 1-coordinate geometry to one Ca(1), one Sn(2), and one P(1) atom. In the sixth O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one P(1) atom. In the seventh O site, O(4) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom.
CaSn3(P2O7)2 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. Both Ca(1)-O(1) bond lengths are 2.47 Å. Both Ca(1)-O(2) bond lengths are 2.39 Å. Both Ca(1)-O(3) bond lengths are 3.01 Å. Both Ca(1)-O(5) bond lengths are 3.05 Å. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 3-coordinate geometry to one O(3), one O(5), and one O(7) atom. The Sn(1)-O(3) bond length is 2.37 Å. The Sn(1)-O(5) bond length is 2.24 Å. The Sn(1)-O(7) bond length is 2.17 Å. In the second Sn site, Sn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms to form distorted SnO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra and corners with four equivalent P(2)O4 tetrahedra. Both Sn(2)-O(1) bond lengths are 2.63 Å. Both Sn(2)-O(2) bond lengths are 2.67 Å. Both Sn(2)-O(6) bond lengths are 2.45 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Sn(2)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 55°. The P(1)-O(2) bond length is 1.55 Å. The P(1)-O(3) bond length is 1.54 Å. The P(1)-O(4) bond length is 1.63 Å. The P(1)-O(5) bond length is 1.53 Å. In the second P site, P(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Sn(2)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 53-63°. The P(2)-O(1) bond length is 1.53 Å. The P(2)-O(4) bond length is 1.63 Å. The P(2)-O(6) bond length is 1.52 Å. The P(2)-O(7) bond length is 1.55 Å. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a 2-coordinate geometry to one Ca(1), one Sn(1), and one P(1) atom. In the second O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Sn(2) and one P(2) atom. In the third O site, O(7) is bonded in a 2-coordinate geometry to one Sn(1) and one P(2) atom. In the fourth O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(2), and one P(2) atom. In the fifth O site, O(2) is bonded in a 1-coordinate geometry to one Ca(1), one Sn(2), and one P(1) atom. In the sixth O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one P(1) atom. In the seventh O site, O(4) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom.