MgFe4(AsS)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 8-coordinate geometry to one Fe(2), one Fe(4), one As(2), one As(4), one S(1), one S(2), one S(3), and one S(4) atom. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one As(1), one As(3), one As(4), one S(1), one S(2), and one S(3) atom to form FeAs3S3 octahedra that share  a cornercorner with one As(1)Fe3S tetrahedra,  a cornercorner with one As(3)Fe3S tetrahedra, and edges with two equivalent Fe(3)As3S3 octahedra. In the second Fe site, Fe(2) is bonded in a 7-coordinate geometry to one Mg(1), one As(2), one As(3), one As(4), one S(1), one S(2), and one S(4) atom. In the third Fe site, Fe(3) is bonded to one As(1), one As(2), one As(3), one S(1), one S(3), and one S(4) atom to form FeAs3S3 octahedra that share  a cornercorner with one As(1)Fe3S tetrahedra,  a cornercorner with one As(3)Fe3S tetrahedra, and edges with two equivalent Fe(1)As3S3 octahedra. In the fourth Fe site, Fe(4) is bonded in a 7-coordinate geometry to one Mg(1), one As(1), one As(2), one As(4), one S(2), one S(3), and one S(4) atom. There are four inequivalent As sites. In the first As site, As(1) is bonded to one Fe(1), one Fe(3), one Fe(4), and one S(3) atom to form distorted AsFe3S tetrahedra that share  a cornercorner with one Fe(1)As3S3 octahedra,  a cornercorner with one Fe(3)As3S3 octahedra, and  an edgeedge with one As(3)Fe3S tetrahedra. The corner-sharing octahedral tilt angles range from 70-73°. In the second As site, As(2) is bonded in a 4-coordinate geometry to one Mg(1), one Fe(2), one Fe(3), and one Fe(4) atom. In the third As site, As(3) is bonded to one Fe(1), one Fe(2), one Fe(3), and one S(1) atom to form distorted AsFe3S tetrahedra that share  a cornercorner with one Fe(1)As3S3 octahedra,  a cornercorner with one Fe(3)As3S3 octahedra, and  an edgeedge with one As(1)Fe3S tetrahedra. The corner-sharing octahedral tilt angles range from 70-74°. In the fourth As site, As(4) is bonded in a 4-coordinate geometry to one Mg(1), one Fe(1), one Fe(2), and one Fe(4) atom. There are four inequivalent S sites. In the first S site, S(1) is bonded in a 5-coordinate geometry to one Mg(1), one Fe(1), one Fe(2), one Fe(3), and one As(3) atom. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(1), one Fe(2), and one Fe(4) atom. In the third S site, S(3) is bonded in a 5-coordinate geometry to one Mg(1), one Fe(1), one Fe(3), one Fe(4), and one As(1) atom. In the fourth S site, S(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(2), one Fe(3), and one Fe(4) atom.
MgFe4(AsS)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 8-coordinate geometry to one Fe(2), one Fe(4), one As(2), one As(4), one S(1), one S(2), one S(3), and one S(4) atom. The Mg(1)-Fe(2) bond length is 2.47 Å. The Mg(1)-Fe(4) bond length is 2.47 Å. The Mg(1)-As(2) bond length is 2.51 Å. The Mg(1)-As(4) bond length is 2.53 Å. The Mg(1)-S(1) bond length is 2.59 Å. The Mg(1)-S(2) bond length is 2.33 Å. The Mg(1)-S(3) bond length is 2.54 Å. The Mg(1)-S(4) bond length is 2.33 Å. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one As(1), one As(3), one As(4), one S(1), one S(2), and one S(3) atom to form FeAs3S3 octahedra that share  a cornercorner with one As(1)Fe3S tetrahedra,  a cornercorner with one As(3)Fe3S tetrahedra, and edges with two equivalent Fe(3)As3S3 octahedra. The Fe(1)-As(1) bond length is 2.36 Å. The Fe(1)-As(3) bond length is 2.41 Å. The Fe(1)-As(4) bond length is 2.32 Å. The Fe(1)-S(1) bond length is 2.36 Å. The Fe(1)-S(2) bond length is 2.23 Å. The Fe(1)-S(3) bond length is 2.42 Å. In the second Fe site, Fe(2) is bonded in a 7-coordinate geometry to one Mg(1), one As(2), one As(3), one As(4), one S(1), one S(2), and one S(4) atom. The Fe(2)-As(2) bond length is 2.50 Å. The Fe(2)-As(3) bond length is 2.34 Å. The Fe(2)-As(4) bond length is 2.30 Å. The Fe(2)-S(1) bond length is 2.43 Å. The Fe(2)-S(2) bond length is 2.41 Å. The Fe(2)-S(4) bond length is 2.19 Å. In the third Fe site, Fe(3) is bonded to one As(1), one As(2), one As(3), one S(1), one S(3), and one S(4) atom to form FeAs3S3 octahedra that share  a cornercorner with one As(1)Fe3S tetrahedra,  a cornercorner with one As(3)Fe3S tetrahedra, and edges with two equivalent Fe(1)As3S3 octahedra. The Fe(3)-As(1) bond length is 2.41 Å. The Fe(3)-As(2) bond length is 2.33 Å. The Fe(3)-As(3) bond length is 2.37 Å. The Fe(3)-S(1) bond length is 2.42 Å. The Fe(3)-S(3) bond length is 2.35 Å. The Fe(3)-S(4) bond length is 2.23 Å. In the fourth Fe site, Fe(4) is bonded in a 7-coordinate geometry to one Mg(1), one As(1), one As(2), one As(4), one S(2), one S(3), and one S(4) atom. The Fe(4)-As(1) bond length is 2.33 Å. The Fe(4)-As(2) bond length is 2.29 Å. The Fe(4)-As(4) bond length is 2.50 Å. The Fe(4)-S(2) bond length is 2.19 Å. The Fe(4)-S(3) bond length is 2.44 Å. The Fe(4)-S(4) bond length is 2.40 Å. There are four inequivalent As sites. In the first As site, As(1) is bonded to one Fe(1), one Fe(3), one Fe(4), and one S(3) atom to form distorted AsFe3S tetrahedra that share  a cornercorner with one Fe(1)As3S3 octahedra,  a cornercorner with one Fe(3)As3S3 octahedra, and  an edgeedge with one As(3)Fe3S tetrahedra. The corner-sharing octahedral tilt angles range from 70-73°. The As(1)-S(3) bond length is 2.58 Å. In the second As site, As(2) is bonded in a 4-coordinate geometry to one Mg(1), one Fe(2), one Fe(3), and one Fe(4) atom. In the third As site, As(3) is bonded to one Fe(1), one Fe(2), one Fe(3), and one S(1) atom to form distorted AsFe3S tetrahedra that share  a cornercorner with one Fe(1)As3S3 octahedra,  a cornercorner with one Fe(3)As3S3 octahedra, and  an edgeedge with one As(1)Fe3S tetrahedra. The corner-sharing octahedral tilt angles range from 70-74°. The As(3)-S(1) bond length is 2.58 Å. In the fourth As site, As(4) is bonded in a 4-coordinate geometry to one Mg(1), one Fe(1), one Fe(2), and one Fe(4) atom. There are four inequivalent S sites. In the first S site, S(1) is bonded in a 5-coordinate geometry to one Mg(1), one Fe(1), one Fe(2), one Fe(3), and one As(3) atom. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(1), one Fe(2), and one Fe(4) atom. In the third S site, S(3) is bonded in a 5-coordinate geometry to one Mg(1), one Fe(1), one Fe(3), one Fe(4), and one As(1) atom. In the fourth S site, S(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Fe(2), one Fe(3), and one Fe(4) atom.