Rb2TaCuS4 crystallizes in the triclinic P1 space group. There are four inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 8-coordinate geometry to one S(1), one S(3), one S(6), one S(8), two equivalent S(2), and two equivalent S(7) atoms. In the second Rb site, Rb(2) is bonded in a 8-coordinate geometry to one S(2), one S(4), one S(5), one S(7), two equivalent S(1), and two equivalent S(8) atoms. In the third Rb site, Rb(3) is bonded in a 8-coordinate geometry to one S(2), one S(4), one S(5), one S(7), two equivalent S(3), and two equivalent S(6) atoms. In the fourth Rb site, Rb(4) is bonded in a 8-coordinate geometry to one S(1), one S(3), one S(6), one S(8), two equivalent S(4), and two equivalent S(5) atoms. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one S(3), one S(4), one S(5), and one S(6) atom to form TaS4 tetrahedra that share edges with two equivalent Cu(1)S4 tetrahedra. In the second Ta site, Ta(2) is bonded to one S(1), one S(2), one S(7), and one S(8) atom to form TaS4 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(3), one S(4), one S(5), and one S(6) atom to form distorted CuS4 tetrahedra that share edges with two equivalent Ta(1)S4 tetrahedra. In the second Cu site, Cu(2) is bonded to one S(1), one S(2), one S(7), and one S(8) atom to form distorted CuS4 tetrahedra that share edges with two equivalent Ta(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(1), one Rb(4), two equivalent Rb(2), one Ta(2), and one Cu(2) atom. In the second S site, S(2) is bonded in a 6-coordinate geometry to one Rb(2), one Rb(3), two equivalent Rb(1), one Ta(2), and one Cu(2) atom. In the third S site, S(3) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(4), two equivalent Rb(3), one Ta(1), and one Cu(1) 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 Ta(1), and one Cu(1) atom. In the fifth S site, S(5) is bonded in a 6-coordinate geometry to one Rb(2), one Rb(3), two equivalent Rb(4), one Ta(1), and one Cu(1) atom. In the sixth S site, S(6) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(4), two equivalent Rb(3), one Ta(1), and one Cu(1) atom. In the seventh S site, S(7) is bonded in a 6-coordinate geometry to one Rb(2), one Rb(3), two equivalent Rb(1), one Ta(2), and one Cu(2) 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 Ta(2), and one Cu(2) atom.
Rb2TaCuS4 crystallizes in the triclinic P1 space group. There are four inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 8-coordinate geometry to one S(1), one S(3), one S(6), one S(8), two equivalent S(2), and two equivalent S(7) atoms. The Rb(1)-S(1) bond length is 3.76 Å. The Rb(1)-S(3) bond length is 3.50 Å. The Rb(1)-S(6) bond length is 3.59 Å. The Rb(1)-S(8) bond length is 3.82 Å. There is one shorter (3.54 Å) and one longer (3.56 Å) Rb(1)-S(2) bond length. There is one shorter (3.49 Å) and one longer (3.63 Å) Rb(1)-S(7) bond length. In the second Rb site, Rb(2) is bonded in a 8-coordinate geometry to one S(2), one S(4), one S(5), one S(7), two equivalent S(1), and two equivalent S(8) atoms. The Rb(2)-S(2) bond length is 3.72 Å. The Rb(2)-S(4) bond length is 3.60 Å. The Rb(2)-S(5) bond length is 3.55 Å. The Rb(2)-S(7) bond length is 3.76 Å. There is one shorter (3.44 Å) and one longer (3.65 Å) Rb(2)-S(1) bond length. There is one shorter (3.56 Å) and one longer (3.58 Å) Rb(2)-S(8) bond length. In the third Rb site, Rb(3) is bonded in a 8-coordinate geometry to one S(2), one S(4), one S(5), one S(7), two equivalent S(3), and two equivalent S(6) atoms. The Rb(3)-S(2) bond length is 3.57 Å. The Rb(3)-S(4) bond length is 3.72 Å. The Rb(3)-S(5) bond length is 3.78 Å. The Rb(3)-S(7) bond length is 3.52 Å. There is one shorter (3.57 Å) and one longer (3.63 Å) Rb(3)-S(3) bond length. There is one shorter (3.51 Å) and one longer (3.57 Å) Rb(3)-S(6) bond length. In the fourth Rb site, Rb(4) is bonded in a 8-coordinate geometry to one S(1), one S(3), one S(6), one S(8), two equivalent S(4), and two equivalent S(5) atoms. The Rb(4)-S(1) bond length is 3.56 Å. The Rb(4)-S(3) bond length is 3.76 Å. The Rb(4)-S(6) bond length is 3.68 Å. The Rb(4)-S(8) bond length is 3.53 Å. There is one shorter (3.50 Å) and one longer (3.56 Å) Rb(4)-S(4) bond length. There is one shorter (3.58 Å) and one longer (3.61 Å) Rb(4)-S(5) bond length. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one S(3), one S(4), one S(5), and one S(6) atom to form TaS4 tetrahedra that share edges with two equivalent Cu(1)S4 tetrahedra. The Ta(1)-S(3) bond length is 2.24 Å. The Ta(1)-S(4) bond length is 2.39 Å. The Ta(1)-S(5) bond length is 2.26 Å. The Ta(1)-S(6) bond length is 2.31 Å. In the second Ta site, Ta(2) is bonded to one S(1), one S(2), one S(7), and one S(8) atom to form TaS4 tetrahedra that share edges with two equivalent Cu(2)S4 tetrahedra. The Ta(2)-S(1) bond length is 2.24 Å. The Ta(2)-S(2) bond length is 2.35 Å. The Ta(2)-S(7) bond length is 2.32 Å. The Ta(2)-S(8) bond length is 2.33 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one S(3), one S(4), one S(5), and one S(6) atom to form distorted CuS4 tetrahedra that share edges with two equivalent Ta(1)S4 tetrahedra. The Cu(1)-S(3) bond length is 2.39 Å. The Cu(1)-S(4) bond length is 2.32 Å. The Cu(1)-S(5) bond length is 2.30 Å. The Cu(1)-S(6) bond length is 2.35 Å. In the second Cu site, Cu(2) is bonded to one S(1), one S(2), one S(7), and one S(8) atom to form distorted CuS4 tetrahedra that share edges with two equivalent Ta(2)S4 tetrahedra. The Cu(2)-S(1) bond length is 2.42 Å. The Cu(2)-S(2) bond length is 2.40 Å. The Cu(2)-S(7) bond length is 2.31 Å. The Cu(2)-S(8) bond length is 2.37 Å. There are eight inequivalent S sites. In the first S site, S(1) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(4), two equivalent Rb(2), one Ta(2), and one Cu(2) atom. In the second S site, S(2) is bonded in a 6-coordinate geometry to one Rb(2), one Rb(3), two equivalent Rb(1), one Ta(2), and one Cu(2) atom. In the third S site, S(3) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(4), two equivalent Rb(3), one Ta(1), and one Cu(1) 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 Ta(1), and one Cu(1) atom. In the fifth S site, S(5) is bonded in a 6-coordinate geometry to one Rb(2), one Rb(3), two equivalent Rb(4), one Ta(1), and one Cu(1) atom. In the sixth S site, S(6) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(4), two equivalent Rb(3), one Ta(1), and one Cu(1) atom. In the seventh S site, S(7) is bonded in a 6-coordinate geometry to one Rb(2), one Rb(3), two equivalent Rb(1), one Ta(2), and one Cu(2) 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 Ta(2), and one Cu(2) atom.