Fe(GeO3)2 crystallizes in the monoclinic P2_1/c space group. Fe(1) is bonded to one O(3), one O(4), two equivalent O(5), and two equivalent O(6) atoms to form distorted FeO6 octahedra that share corners with three equivalent Ge(1)O4 tetrahedra, corners with two equivalent Ge(2)O5 trigonal bipyramids, edges with two equivalent Fe(1)O6 octahedra, and  an edgeedge with one Ge(2)O5 trigonal bipyramid. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one O(4), one O(5), and two equivalent O(2) atoms to form GeO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra and corners with two equivalent Ge(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-58°. In the second Ge site, Ge(2) is bonded to one O(6), two equivalent O(1), and two equivalent O(3) atoms to form distorted GeO5 trigonal bipyramids that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Ge(2)O5 trigonal bipyramids,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Ge(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 30-43°. There are six inequivalent O sites. In the first O site, O(6) is bonded in a trigonal non-coplanar geometry to two equivalent Fe(1) and one Ge(2) atom. In the second O site, O(1) is bonded in a bent 120 degrees geometry to two equivalent Ge(2) atoms. In the third O site, O(2) is bonded in a bent 120 degrees geometry to two equivalent Ge(1) atoms. In the fourth O site, O(3) is bonded in a distorted T-shaped geometry to one Fe(1) and two equivalent Ge(2) atoms. In the fifth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one Ge(1) atom. In the sixth O site, O(5) is bonded in a trigonal planar geometry to two equivalent Fe(1) and one Ge(1) atom.
Fe(GeO3)2 crystallizes in the monoclinic P2_1/c space group. Fe(1) is bonded to one O(3), one O(4), two equivalent O(5), and two equivalent O(6) atoms to form distorted FeO6 octahedra that share corners with three equivalent Ge(1)O4 tetrahedra, corners with two equivalent Ge(2)O5 trigonal bipyramids, edges with two equivalent Fe(1)O6 octahedra, and  an edgeedge with one Ge(2)O5 trigonal bipyramid. The Fe(1)-O(3) bond length is 2.04 Å. The Fe(1)-O(4) bond length is 1.86 Å. There is one shorter (1.99 Å) and one longer (2.10 Å) Fe(1)-O(5) bond length. There is one shorter (1.98 Å) and one longer (1.99 Å) Fe(1)-O(6) bond length. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one O(4), one O(5), and two equivalent O(2) atoms to form GeO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra and corners with two equivalent Ge(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-58°. The Ge(1)-O(4) bond length is 1.75 Å. The Ge(1)-O(5) bond length is 1.80 Å. Both Ge(1)-O(2) bond lengths are 1.75 Å. In the second Ge site, Ge(2) is bonded to one O(6), two equivalent O(1), and two equivalent O(3) atoms to form distorted GeO5 trigonal bipyramids that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Ge(2)O5 trigonal bipyramids,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Ge(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 30-43°. The Ge(2)-O(6) bond length is 1.87 Å. There is one shorter (1.78 Å) and one longer (1.80 Å) Ge(2)-O(1) bond length. There is one shorter (1.84 Å) and one longer (2.08 Å) Ge(2)-O(3) bond length. There are six inequivalent O sites. In the first O site, O(6) is bonded in a trigonal non-coplanar geometry to two equivalent Fe(1) and one Ge(2) atom. In the second O site, O(1) is bonded in a bent 120 degrees geometry to two equivalent Ge(2) atoms. In the third O site, O(2) is bonded in a bent 120 degrees geometry to two equivalent Ge(1) atoms. In the fourth O site, O(3) is bonded in a distorted T-shaped geometry to one Fe(1) and two equivalent Ge(2) atoms. In the fifth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one Ge(1) atom. In the sixth O site, O(5) is bonded in a trigonal planar geometry to two equivalent Fe(1) and one Ge(1) atom.