CaSnO2 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted CaO6 pentagonal pyramids that share corners with four equivalent Ca(2)O5 trigonal bipyramids,  an edgeedge with one Ca(2)O5 trigonal bipyramid, and faces with two equivalent Ca(1)O6 pentagonal pyramids. In the second Ca site, Ca(2) is bonded to one O(3), two equivalent O(2), and two equivalent O(4) atoms to form distorted CaO5 trigonal bipyramids that share corners with four equivalent Ca(1)O6 pentagonal pyramids,  an edgeedge with one Ca(1)O6 pentagonal pyramid, and edges with two equivalent Ca(2)O5 trigonal bipyramids. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a T-shaped geometry to one O(1), one O(2), and one O(3) atom. In the second Sn site, Sn(2) is bonded in a 3-coordinate geometry to one O(1), one O(2), and one O(4) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ca(1), one Sn(1), and one Sn(2) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Ca(2), one Sn(1), and one Sn(2) atom. In the third O site, O(3) is bonded to one Ca(2), two equivalent Ca(1), and one Sn(1) atom to form OCa3Sn tetrahedra that share corners with four equivalent O(4)Ca4Sn square pyramids, corners with two equivalent O(3)Ca3Sn tetrahedra, and  an edgeedge with one O(4)Ca4Sn square pyramid. In the fourth O site, O(4) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Sn(2) atom to form OCa4Sn square pyramids that share corners with four equivalent O(3)Ca3Sn tetrahedra, edges with two equivalent O(4)Ca4Sn square pyramids, and  an edgeedge with one O(3)Ca3Sn tetrahedra.
CaSnO2 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted CaO6 pentagonal pyramids that share corners with four equivalent Ca(2)O5 trigonal bipyramids,  an edgeedge with one Ca(2)O5 trigonal bipyramid, and faces with two equivalent Ca(1)O6 pentagonal pyramids. There is one shorter (2.49 Å) and one longer (2.52 Å) Ca(1)-O(1) bond length. Both Ca(1)-O(3) bond lengths are 2.36 Å. There is one shorter (2.35 Å) and one longer (2.56 Å) Ca(1)-O(4) bond length. In the second Ca site, Ca(2) is bonded to one O(3), two equivalent O(2), and two equivalent O(4) atoms to form distorted CaO5 trigonal bipyramids that share corners with four equivalent Ca(1)O6 pentagonal pyramids,  an edgeedge with one Ca(1)O6 pentagonal pyramid, and edges with two equivalent Ca(2)O5 trigonal bipyramids. The Ca(2)-O(3) bond length is 2.37 Å. There is one shorter (2.33 Å) and one longer (2.40 Å) Ca(2)-O(2) bond length. There is one shorter (2.33 Å) and one longer (2.34 Å) Ca(2)-O(4) bond length. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a T-shaped geometry to one O(1), one O(2), and one O(3) atom. The Sn(1)-O(1) bond length is 2.27 Å. The Sn(1)-O(2) bond length is 2.43 Å. The Sn(1)-O(3) bond length is 2.06 Å. In the second Sn site, Sn(2) is bonded in a 3-coordinate geometry to one O(1), one O(2), and one O(4) atom. The Sn(2)-O(1) bond length is 2.11 Å. The Sn(2)-O(2) bond length is 2.10 Å. The Sn(2)-O(4) bond length is 2.39 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ca(1), one Sn(1), and one Sn(2) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Ca(2), one Sn(1), and one Sn(2) atom. In the third O site, O(3) is bonded to one Ca(2), two equivalent Ca(1), and one Sn(1) atom to form OCa3Sn tetrahedra that share corners with four equivalent O(4)Ca4Sn square pyramids, corners with two equivalent O(3)Ca3Sn tetrahedra, and  an edgeedge with one O(4)Ca4Sn square pyramid. In the fourth O site, O(4) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Sn(2) atom to form OCa4Sn square pyramids that share corners with four equivalent O(3)Ca3Sn tetrahedra, edges with two equivalent O(4)Ca4Sn square pyramids, and  an edgeedge with one O(3)Ca3Sn tetrahedra.