Fe2CPH2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), one O(3), one O(5), and two equivalent O(4) atoms to form distorted FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra, and  an edgeedge with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-59°. In the second Fe site, Fe(2) is bonded to one O(2), one O(4), one O(5), one O(7), and two equivalent O(6) atoms to form distorted FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-59°. C(1) is bonded in a distorted bent 120 degrees geometry to one O(5) and one O(7) atom. P(1) is bonded to one O(1), one O(2), one O(4), and one O(6) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-57°. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(1) and one O(3) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(3) and one O(7) atom. There are seven inequivalent O sites. In the first O site, O(3) is bonded in a distorted water-like geometry to one Fe(1), one H(1), and one H(2) atom. In the second O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Fe(2), two equivalent Fe(1), and one P(1) atom. In the third O site, O(5) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one C(1) atom. In the fourth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Fe(2) and one P(1) atom. In the fifth O site, O(7) is bonded in a 3-coordinate geometry to one Fe(2), one C(1), and one H(2) atom. In the sixth O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Fe(1), one P(1), and one H(1) atom. In the seventh O site, O(2) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one P(1) atom.
Fe2CPH2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), one O(3), one O(5), and two equivalent O(4) atoms to form distorted FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra, and  an edgeedge with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-59°. The Fe(1)-O(1) bond length is 2.09 Å. The Fe(1)-O(2) bond length is 2.21 Å. The Fe(1)-O(3) bond length is 2.09 Å. The Fe(1)-O(5) bond length is 2.38 Å. There is one shorter (2.05 Å) and one longer (2.52 Å) Fe(1)-O(4) bond length. In the second Fe site, Fe(2) is bonded to one O(2), one O(4), one O(5), one O(7), and two equivalent O(6) atoms to form distorted FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-59°. The Fe(2)-O(2) bond length is 2.16 Å. The Fe(2)-O(4) bond length is 2.36 Å. The Fe(2)-O(5) bond length is 2.17 Å. The Fe(2)-O(7) bond length is 2.19 Å. There is one shorter (2.06 Å) and one longer (2.18 Å) Fe(2)-O(6) bond length. C(1) is bonded in a distorted bent 120 degrees geometry to one O(5) and one O(7) atom. The C(1)-O(5) bond length is 1.28 Å. The C(1)-O(7) bond length is 1.26 Å. P(1) is bonded to one O(1), one O(2), one O(4), and one O(6) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-57°. The P(1)-O(1) bond length is 1.54 Å. The P(1)-O(2) bond length is 1.55 Å. The P(1)-O(4) bond length is 1.58 Å. The P(1)-O(6) bond length is 1.56 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(1) and one O(3) atom. The H(1)-O(1) bond length is 1.73 Å. The H(1)-O(3) bond length is 1.00 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(3) and one O(7) atom. The H(2)-O(3) bond length is 0.99 Å. The H(2)-O(7) bond length is 1.74 Å. There are seven inequivalent O sites. In the first O site, O(3) is bonded in a distorted water-like geometry to one Fe(1), one H(1), and one H(2) atom. In the second O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Fe(2), two equivalent Fe(1), and one P(1) atom. In the third O site, O(5) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one C(1) atom. In the fourth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Fe(2) and one P(1) atom. In the fifth O site, O(7) is bonded in a 3-coordinate geometry to one Fe(2), one C(1), and one H(2) atom. In the sixth O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Fe(1), one P(1), and one H(1) atom. In the seventh O site, O(2) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one P(1) atom.