RbBiSiS4 crystallizes in the monoclinic P2_1/c space group. Rb(1) is bonded in a 8-coordinate geometry to one S(2), two equivalent S(1), two equivalent S(4), and three equivalent S(3) atoms. Si(1) is bonded in a tetrahedral geometry to one S(1), one S(2), one S(3), and one S(4) atom. Bi(1) is bonded in a 5-coordinate geometry to one S(1), one S(3), one S(4), and two equivalent S(2) atoms. There are four inequivalent S sites. In the first S site, S(1) is bonded in a 1-coordinate geometry to two equivalent Rb(1), one Si(1), and one Bi(1) atom. In the second S site, S(2) is bonded in a distorted see-saw-like geometry to one Rb(1), one Si(1), and two equivalent Bi(1) atoms. In the third S site, S(3) is bonded to three equivalent Rb(1), one Si(1), and one Bi(1) atom to form a mixture of distorted corner and edge-sharing SRb3SiBi trigonal bipyramids. In the fourth S site, S(4) is bonded in a distorted single-bond geometry to two equivalent Rb(1), one Si(1), and one Bi(1) atom.
RbBiSiS4 crystallizes in the monoclinic P2_1/c space group. Rb(1) is bonded in a 8-coordinate geometry to one S(2), two equivalent S(1), two equivalent S(4), and three equivalent S(3) atoms. The Rb(1)-S(2) bond length is 3.41 Å. There is one shorter (3.63 Å) and one longer (3.67 Å) Rb(1)-S(1) bond length. There is one shorter (3.49 Å) and one longer (3.54 Å) Rb(1)-S(4) bond length. There are a spread of Rb(1)-S(3) bond distances ranging from 3.46-3.61 Å. Si(1) is bonded in a tetrahedral geometry to one S(1), one S(2), one S(3), and one S(4) atom. The Si(1)-S(1) bond length is 2.14 Å. The Si(1)-S(2) bond length is 2.17 Å. The Si(1)-S(3) bond length is 2.13 Å. The Si(1)-S(4) bond length is 2.12 Å. Bi(1) is bonded in a 5-coordinate geometry to one S(1), one S(3), one S(4), and two equivalent S(2) atoms. The Bi(1)-S(1) bond length is 2.74 Å. The Bi(1)-S(3) bond length is 2.82 Å. The Bi(1)-S(4) bond length is 2.89 Å. There is one shorter (2.76 Å) and one longer (2.99 Å) Bi(1)-S(2) bond length. There are four inequivalent S sites. In the first S site, S(1) is bonded in a 1-coordinate geometry to two equivalent Rb(1), one Si(1), and one Bi(1) atom. In the second S site, S(2) is bonded in a distorted see-saw-like geometry to one Rb(1), one Si(1), and two equivalent Bi(1) atoms. In the third S site, S(3) is bonded to three equivalent Rb(1), one Si(1), and one Bi(1) atom to form a mixture of distorted corner and edge-sharing SRb3SiBi trigonal bipyramids. In the fourth S site, S(4) is bonded in a distorted single-bond geometry to two equivalent Rb(1), one Si(1), and one Bi(1) atom.