Rb4MgNb2(CuS4)2 crystallizes in the triclinic P1 space group. There are four inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 9-coordinate geometry to one Mg(1), one S(2), one S(3), one S(5), one S(8), two equivalent S(6), and two equivalent S(7) atoms. In the second Rb site, Rb(2) is bonded in a 7-coordinate geometry to one S(1), one S(4), one S(6), two equivalent S(5), and two equivalent S(8) atoms. In the third Rb site, Rb(3) is bonded in a 6-coordinate geometry to one S(1), one S(4), two equivalent S(2), and two equivalent S(3) atoms. In the fourth Rb site, Rb(4) is bonded in a 7-coordinate geometry to one S(2), one S(5), one S(8), two equivalent S(1), and two equivalent S(4) atoms. Mg(1) is bonded in a 3-coordinate geometry to one Rb(1), one S(3), one S(6), and one S(7) atom. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one S(5), one S(6), one S(7), and one S(8) atom to form NbS4 tetrahedra that share edges with two equivalent Cu(1)S4 tetrahedra. In the second Nb site, Nb(2) is bonded to one S(1), one S(2), one S(3), and one S(4) atom to form NbS4 tetrahedra that share edges with two equivalent Cu(2)S4 tetrahedra. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one S(5), one S(6), one S(7), and one S(8) atom to form distorted CuS4 tetrahedra that share edges with two equivalent Nb(1)S4 tetrahedra. In the second Cu site, Cu(2) is bonded to one S(1), one S(2), one S(3), and one S(4) atom to form distorted CuS4 tetrahedra that share edges with two equivalent Nb(2)S4 tetrahedra. There are eight inequivalent S sites. In the first S site, S(1) is bonded in a 6-coordinate geometry to one Rb(2), one Rb(3), two equivalent Rb(4), one Nb(2), and one Cu(2) atom. In the second S site, S(2) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(4), two equivalent Rb(3), one Nb(2), and one Cu(2) atom. In the third S site, S(3) is bonded in a 3-coordinate geometry to one Rb(1), two equivalent Rb(3), one Mg(1), one Nb(2), and one Cu(2) atom. In the fourth S site, S(4) is bonded in a 6-coordinate geometry to one Rb(2), one Rb(3), two equivalent Rb(4), one Nb(2), and one Cu(2) atom. In the fifth S site, S(5) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(4), two equivalent Rb(2), one Nb(1), and one Cu(1) atom. In the sixth S site, S(6) is bonded in a 6-coordinate geometry to one Rb(2), two equivalent Rb(1), one Mg(1), one Nb(1), and one Cu(1) atom. In the seventh S site, S(7) is bonded in a 4-coordinate geometry to two equivalent Rb(1), one Mg(1), one Nb(1), and one Cu(1) atom. In the eighth S site, S(8) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(4), two equivalent Rb(2), one Nb(1), and one Cu(1) atom.
Rb4MgNb2(CuS4)2 crystallizes in the triclinic P1 space group. There are four inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 9-coordinate geometry to one Mg(1), one S(2), one S(3), one S(5), one S(8), two equivalent S(6), and two equivalent S(7) atoms. The Rb(1)-Mg(1) bond length is 3.61 Å. The Rb(1)-S(2) bond length is 3.55 Å. The Rb(1)-S(3) bond length is 3.82 Å. The Rb(1)-S(5) bond length is 3.51 Å. The Rb(1)-S(8) bond length is 3.81 Å. There is one shorter (3.30 Å) and one longer (3.53 Å) Rb(1)-S(6) bond length. There is one shorter (3.53 Å) and one longer (3.91 Å) Rb(1)-S(7) bond length. In the second Rb site, Rb(2) is bonded in a 7-coordinate geometry to one S(1), one S(4), one S(6), two equivalent S(5), and two equivalent S(8) atoms. The Rb(2)-S(1) bond length is 3.51 Å. The Rb(2)-S(4) bond length is 3.59 Å. The Rb(2)-S(6) bond length is 3.66 Å. There is one shorter (3.52 Å) and one longer (3.60 Å) Rb(2)-S(5) bond length. There is one shorter (3.55 Å) and one longer (3.71 Å) Rb(2)-S(8) bond length. In the third Rb site, Rb(3) is bonded in a 6-coordinate geometry to one S(1), one S(4), two equivalent S(2), and two equivalent S(3) atoms. The Rb(3)-S(1) bond length is 3.37 Å. The Rb(3)-S(4) bond length is 3.42 Å. There is one shorter (3.38 Å) and one longer (3.74 Å) Rb(3)-S(2) bond length. There is one shorter (3.48 Å) and one longer (3.62 Å) Rb(3)-S(3) bond length. In the fourth Rb site, Rb(4) is bonded in a 7-coordinate geometry to one S(2), one S(5), one S(8), two equivalent S(1), and two equivalent S(4) atoms. The Rb(4)-S(2) bond length is 3.85 Å. The Rb(4)-S(5) bond length is 3.52 Å. The Rb(4)-S(8) bond length is 3.44 Å. There is one shorter (3.67 Å) and one longer (3.72 Å) Rb(4)-S(1) bond length. There is one shorter (3.52 Å) and one longer (3.67 Å) Rb(4)-S(4) bond length. Mg(1) is bonded in a 3-coordinate geometry to one Rb(1), one S(3), one S(6), and one S(7) atom. The Mg(1)-S(3) bond length is 2.50 Å. The Mg(1)-S(6) bond length is 2.43 Å. The Mg(1)-S(7) bond length is 2.44 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one S(5), one S(6), one S(7), and one S(8) atom to form NbS4 tetrahedra that share edges with two equivalent Cu(1)S4 tetrahedra. The Nb(1)-S(5) bond length is 2.36 Å. The Nb(1)-S(6) bond length is 2.41 Å. The Nb(1)-S(7) bond length is 2.38 Å. The Nb(1)-S(8) bond length is 2.31 Å. In the second Nb site, Nb(2) is bonded to one S(1), one S(2), one S(3), and one S(4) atom to form NbS4 tetrahedra that share edges with two equivalent Cu(2)S4 tetrahedra. The Nb(2)-S(1) bond length is 2.32 Å. The Nb(2)-S(2) bond length is 2.33 Å. The Nb(2)-S(3) bond length is 2.38 Å. The Nb(2)-S(4) bond length is 2.32 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one S(5), one S(6), one S(7), and one S(8) atom to form distorted CuS4 tetrahedra that share edges with two equivalent Nb(1)S4 tetrahedra. The Cu(1)-S(5) bond length is 2.28 Å. The Cu(1)-S(6) bond length is 2.46 Å. The Cu(1)-S(7) bond length is 2.49 Å. The Cu(1)-S(8) bond length is 2.33 Å. In the second Cu site, Cu(2) is bonded to one S(1), one S(2), one S(3), and one S(4) atom to form distorted CuS4 tetrahedra that share edges with two equivalent Nb(2)S4 tetrahedra. The Cu(2)-S(1) bond length is 2.35 Å. The Cu(2)-S(2) bond length is 2.36 Å. The Cu(2)-S(3) bond length is 2.51 Å. The Cu(2)-S(4) bond length is 2.34 Å. There are eight inequivalent S sites. In the first S site, S(1) is bonded in a 6-coordinate geometry to one Rb(2), one Rb(3), two equivalent Rb(4), one Nb(2), and one Cu(2) atom. In the second S site, S(2) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(4), two equivalent Rb(3), one Nb(2), and one Cu(2) atom. In the third S site, S(3) is bonded in a 3-coordinate geometry to one Rb(1), two equivalent Rb(3), one Mg(1), one Nb(2), and one Cu(2) atom. In the fourth S site, S(4) is bonded in a 6-coordinate geometry to one Rb(2), one Rb(3), two equivalent Rb(4), one Nb(2), and one Cu(2) atom. In the fifth S site, S(5) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(4), two equivalent Rb(2), one Nb(1), and one Cu(1) atom. In the sixth S site, S(6) is bonded in a 6-coordinate geometry to one Rb(2), two equivalent Rb(1), one Mg(1), one Nb(1), and one Cu(1) atom. In the seventh S site, S(7) is bonded in a 4-coordinate geometry to two equivalent Rb(1), one Mg(1), one Nb(1), and one Cu(1) atom. In the eighth S site, S(8) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(4), two equivalent Rb(2), one Nb(1), and one Cu(1) atom.