Nd2PbSi2S8 crystallizes in the monoclinic Cc space group. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 8-coordinate geometry to one S(1), one S(2), one S(3), one S(6), one S(7), one S(8), and two equivalent S(4) atoms. In the second Nd site, Nd(2) is bonded in a 8-coordinate geometry to one S(3), one S(6), one S(7), one S(8), two equivalent S(2), and two equivalent S(5) atoms. Pb(1) is bonded in a 6-coordinate geometry to one S(5), one S(6), one S(7), one S(8), and two equivalent S(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to one S(1), one S(2), one S(3), and one S(7) atom. In the second Si site, Si(2) is bonded in a tetrahedral geometry to one S(4), one S(5), one S(6), and one S(8) atom. There are eight inequivalent S sites. In the first S site, S(7) is bonded in a 3-coordinate geometry to one Nd(1), one Nd(2), one Pb(1), and one Si(1) atom. In the second S site, S(8) is bonded in a 3-coordinate geometry to one Nd(1), one Nd(2), one Pb(1), and one Si(2) atom. In the third S site, S(1) is bonded in a distorted single-bond geometry to one Nd(1), two equivalent Pb(1), and one Si(1) atom. In the fourth S site, S(2) is bonded to one Nd(1), two equivalent Nd(2), and one Si(1) atom to form distorted SNd3Si trigonal pyramids that share corners with two equivalent S(5)Nd2SiPb trigonal pyramids, corners with two equivalent S(2)Nd3Si trigonal pyramids, and  an edgeedge with one S(5)Nd2SiPb trigonal pyramid. In the fifth S site, S(3) is bonded in a distorted T-shaped geometry to one Nd(1), one Nd(2), and one Si(1) atom. In the sixth S site, S(4) is bonded in a distorted T-shaped geometry to two equivalent Nd(1) and one Si(2) atom. In the seventh S site, S(5) is bonded to two equivalent Nd(2), one Pb(1), and one Si(2) atom to form distorted SNd2SiPb trigonal pyramids that share corners with two equivalent S(5)Nd2SiPb trigonal pyramids, corners with two equivalent S(2)Nd3Si trigonal pyramids, and  an edgeedge with one S(2)Nd3Si trigonal pyramid. In the eighth S site, S(6) is bonded in a 4-coordinate geometry to one Nd(1), one Nd(2), one Pb(1), and one Si(2) atom.
Nd2PbSi2S8 crystallizes in the monoclinic Cc space group. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 8-coordinate geometry to one S(1), one S(2), one S(3), one S(6), one S(7), one S(8), and two equivalent S(4) atoms. The Nd(1)-S(1) bond length is 3.12 Å. The Nd(1)-S(2) bond length is 2.92 Å. The Nd(1)-S(3) bond length is 2.97 Å. The Nd(1)-S(6) bond length is 3.08 Å. The Nd(1)-S(7) bond length is 3.08 Å. The Nd(1)-S(8) bond length is 3.09 Å. There is one shorter (2.82 Å) and one longer (2.90 Å) Nd(1)-S(4) bond length. In the second Nd site, Nd(2) is bonded in a 8-coordinate geometry to one S(3), one S(6), one S(7), one S(8), two equivalent S(2), and two equivalent S(5) atoms. The Nd(2)-S(3) bond length is 2.82 Å. The Nd(2)-S(6) bond length is 2.88 Å. The Nd(2)-S(7) bond length is 3.02 Å. The Nd(2)-S(8) bond length is 3.01 Å. There is one shorter (2.96 Å) and one longer (3.22 Å) Nd(2)-S(2) bond length. There is one shorter (3.04 Å) and one longer (3.17 Å) Nd(2)-S(5) bond length. Pb(1) is bonded in a 6-coordinate geometry to one S(5), one S(6), one S(7), one S(8), and two equivalent S(1) atoms. The Pb(1)-S(5) bond length is 2.88 Å. The Pb(1)-S(6) bond length is 3.13 Å. The Pb(1)-S(7) bond length is 3.24 Å. The Pb(1)-S(8) bond length is 3.28 Å. There is one shorter (2.84 Å) and one longer (3.15 Å) Pb(1)-S(1) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to one S(1), one S(2), one S(3), and one S(7) atom. The Si(1)-S(1) bond length is 2.13 Å. The Si(1)-S(2) bond length is 2.15 Å. The Si(1)-S(3) bond length is 2.13 Å. The Si(1)-S(7) bond length is 2.14 Å. In the second Si site, Si(2) is bonded in a tetrahedral geometry to one S(4), one S(5), one S(6), and one S(8) atom. The Si(2)-S(4) bond length is 2.14 Å. The Si(2)-S(5) bond length is 2.13 Å. The Si(2)-S(6) bond length is 2.14 Å. The Si(2)-S(8) bond length is 2.13 Å. There are eight inequivalent S sites. In the first S site, S(7) is bonded in a 3-coordinate geometry to one Nd(1), one Nd(2), one Pb(1), and one Si(1) atom. In the second S site, S(8) is bonded in a 3-coordinate geometry to one Nd(1), one Nd(2), one Pb(1), and one Si(2) atom. In the third S site, S(1) is bonded in a distorted single-bond geometry to one Nd(1), two equivalent Pb(1), and one Si(1) atom. In the fourth S site, S(2) is bonded to one Nd(1), two equivalent Nd(2), and one Si(1) atom to form distorted SNd3Si trigonal pyramids that share corners with two equivalent S(5)Nd2SiPb trigonal pyramids, corners with two equivalent S(2)Nd3Si trigonal pyramids, and  an edgeedge with one S(5)Nd2SiPb trigonal pyramid. In the fifth S site, S(3) is bonded in a distorted T-shaped geometry to one Nd(1), one Nd(2), and one Si(1) atom. In the sixth S site, S(4) is bonded in a distorted T-shaped geometry to two equivalent Nd(1) and one Si(2) atom. In the seventh S site, S(5) is bonded to two equivalent Nd(2), one Pb(1), and one Si(2) atom to form distorted SNd2SiPb trigonal pyramids that share corners with two equivalent S(5)Nd2SiPb trigonal pyramids, corners with two equivalent S(2)Nd3Si trigonal pyramids, and  an edgeedge with one S(2)Nd3Si trigonal pyramid. In the eighth S site, S(6) is bonded in a 4-coordinate geometry to one Nd(1), one Nd(2), one Pb(1), and one Si(2) atom.