Fe(Sn2Se5)2(N(CH3)4)2 crystallizes in the tetragonal I-4 space group. The structure consists of four tetramethylammonium molecules inside a Fe(Sn2Se5)2 framework. In the Fe(Sn2Se5)2 framework, Fe(1) is bonded to four equivalent Se(3) atoms to form FeSe4 tetrahedra that share corners with four equivalent Sn(1)Se4 tetrahedra. Sn(1) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form SnSe4 tetrahedra that share  a cornercorner with one Fe(1)Se4 tetrahedra and corners with three equivalent Sn(1)Se4 tetrahedra. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a water-like geometry to two equivalent Sn(1) atoms. In the second Se site, Se(2) is bonded in a water-like geometry to two equivalent Sn(1) atoms. In the third Se site, Se(3) is bonded in a bent 120 degrees geometry to one Fe(1) and one Sn(1) atom.
Fe(Sn2Se5)2(N(CH3)4)2 crystallizes in the tetragonal I-4 space group. The structure consists of four tetramethylammonium molecules inside a Fe(Sn2Se5)2 framework. In the Fe(Sn2Se5)2 framework, Fe(1) is bonded to four equivalent Se(3) atoms to form FeSe4 tetrahedra that share corners with four equivalent Sn(1)Se4 tetrahedra. All Fe(1)-Se(3) bond lengths are 2.41 Å. Sn(1) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form SnSe4 tetrahedra that share  a cornercorner with one Fe(1)Se4 tetrahedra and corners with three equivalent Sn(1)Se4 tetrahedra. The Sn(1)-Se(2) bond length is 2.59 Å. The Sn(1)-Se(3) bond length is 2.54 Å. There is one shorter (2.59 Å) and one longer (2.61 Å) Sn(1)-Se(1) bond length. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a water-like geometry to two equivalent Sn(1) atoms. In the second Se site, Se(2) is bonded in a water-like geometry to two equivalent Sn(1) atoms. In the third Se site, Se(3) is bonded in a bent 120 degrees geometry to one Fe(1) and one Sn(1) atom.