(FeP2O7)2N2 crystallizes in the monoclinic P2_1/c space group. The structure consists of four ammonia atoms inside a FeP2O7 framework. In the FeP2O7 framework, Fe(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 8-45°. In the second P site, P(2) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 15-42°. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom. In the second O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the third O site, O(7) is bonded in a linear geometry to one Fe(1) and one P(1) atom. In the fourth O site, O(1) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the sixth O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one P(2) atom. In the seventh O site, O(4) is bonded in a linear geometry to one Fe(1) and one P(2) atom.
(FeP2O7)2N2 crystallizes in the monoclinic P2_1/c space group. The structure consists of four ammonia atoms inside a FeP2O7 framework. In the FeP2O7 framework, Fe(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. The Fe(1)-O(2) bond length is 2.01 Å. The Fe(1)-O(3) bond length is 2.01 Å. The Fe(1)-O(4) bond length is 1.99 Å. The Fe(1)-O(5) bond length is 2.02 Å. The Fe(1)-O(6) bond length is 2.05 Å. The Fe(1)-O(7) bond length is 1.99 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 8-45°. The P(1)-O(1) bond length is 1.62 Å. The P(1)-O(2) bond length is 1.52 Å. The P(1)-O(6) bond length is 1.54 Å. The P(1)-O(7) bond length is 1.52 Å. In the second P site, P(2) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 15-42°. The P(2)-O(1) bond length is 1.62 Å. The P(2)-O(3) bond length is 1.53 Å. The P(2)-O(4) bond length is 1.51 Å. The P(2)-O(5) bond length is 1.52 Å. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom. In the second O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the third O site, O(7) is bonded in a linear geometry to one Fe(1) and one P(1) atom. In the fourth O site, O(1) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the sixth O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one P(2) atom. In the seventh O site, O(4) is bonded in a linear geometry to one Fe(1) and one P(2) atom.