Pr4(ErS2)11 crystallizes in the monoclinic C2/m space group. There are six inequivalent Er sites. In the first Er site, Er(1) is bonded to one S(2), one S(9), two equivalent S(8), and three equivalent S(11) atoms to form distorted ErS7 pentagonal bipyramids that share  a cornercorner with one Er(4)S6 octahedra, corners with two equivalent Er(3)S6 octahedra, edges with two equivalent Er(4)S6 octahedra, and edges with four equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 39-50°. In the second Er site, Er(2) is bonded to one S(4), one S(7), two equivalent S(1), and two equivalent S(10) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles range from 49-59°. In the third Er site, Er(3) is bonded to one S(3), one S(6), two equivalent S(5), and two equivalent S(9) atoms to form ErS6 octahedra that share corners with three equivalent Er(4)S6 octahedra, corners with two equivalent Er(1)S7 pentagonal bipyramids, edges with two equivalent Er(3)S6 octahedra, and edges with two equivalent Er(5)S6 octahedra. The corner-sharing octahedral tilt angles range from 51-62°. In the fourth Er site, Er(4) is bonded to one S(11), two equivalent S(2), and three equivalent S(3) atoms to form ErS6 octahedra that share corners with three equivalent Er(3)S6 octahedra,  a cornercorner with one Er(1)S7 pentagonal bipyramid, edges with four equivalent Er(4)S6 octahedra, and edges with two equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 51-62°. In the fifth Er site, Er(5) is bonded to one S(10), one S(5), two equivalent S(4), and two equivalent S(6) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles range from 49-59°. In the sixth Er site, Er(6) is bonded to two equivalent S(10) and four equivalent S(7) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are two inequivalent Pr sites. In the first Pr site, Pr(1) is bonded in a 8-coordinate geometry to one S(1), one S(9), two equivalent S(6), two equivalent S(7), and two equivalent S(8) atoms. In the second Pr site, Pr(2) is bonded in a 8-coordinate geometry to one S(4), one S(8), two equivalent S(1), two equivalent S(2), and two equivalent S(5) atoms. There are eleven inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Er(2), one Pr(1), and two equivalent Pr(2) atoms to form distorted SPr3Er2 trigonal bipyramids that share corners with two equivalent S(6)Pr2Er3 square pyramids, corners with two equivalent S(2)Pr2Er3 trigonal bipyramids, corners with two equivalent S(5)Pr2Er3 trigonal bipyramids,  a cornercorner with one S(9)PrEr3 trigonal pyramid, edges with two equivalent S(7)Pr2Er3 square pyramids,  an edgeedge with one S(2)Pr2Er3 trigonal bipyramid,  an edgeedge with one S(5)Pr2Er3 trigonal bipyramid, edges with two equivalent S(1)Pr3Er2 trigonal bipyramids, and edges with two equivalent S(8)Pr3Er2 trigonal bipyramids. In the second S site, S(2) is bonded to one Er(1), two equivalent Er(4), and two equivalent Pr(2) atoms to form SPr2Er3 trigonal bipyramids that share corners with two equivalent S(5)Pr2Er3 trigonal bipyramids, corners with two equivalent S(1)Pr3Er2 trigonal bipyramids,  a cornercorner with one S(11)Er4 trigonal pyramid,  a cornercorner with one S(9)PrEr3 trigonal pyramid,  an edgeedge with one S(5)Pr2Er3 trigonal bipyramid,  an edgeedge with one S(1)Pr3Er2 trigonal bipyramid, edges with two equivalent S(2)Pr2Er3 trigonal bipyramids, edges with two equivalent S(8)Pr3Er2 trigonal bipyramids, and edges with two equivalent S(11)Er4 trigonal pyramids. In the third S site, S(3) is bonded in a rectangular see-saw-like geometry to one Er(3) and three equivalent Er(4) atoms. In the fourth S site, S(4) is bonded in a 3-coordinate geometry to one Er(2), two equivalent Er(5), and one Pr(2) atom. In the fifth S site, S(5) is bonded to one Er(5), two equivalent Er(3), and two equivalent Pr(2) atoms to form SPr2Er3 trigonal bipyramids that share corners with two equivalent S(2)Pr2Er3 trigonal bipyramids, corners with two equivalent S(1)Pr3Er2 trigonal bipyramids, corners with two equivalent S(8)Pr3Er2 trigonal bipyramids, corners with two equivalent S(9)PrEr3 trigonal pyramids, edges with two equivalent S(6)Pr2Er3 square pyramids,  an edgeedge with one S(2)Pr2Er3 trigonal bipyramid,  an edgeedge with one S(1)Pr3Er2 trigonal bipyramid, edges with two equivalent S(5)Pr2Er3 trigonal bipyramids, and  an edgeedge with one S(9)PrEr3 trigonal pyramid. In the sixth S site, S(6) is bonded to one Er(3), two equivalent Er(5), and two equivalent Pr(1) atoms to form SPr2Er3 square pyramids that share corners with two equivalent S(7)Pr2Er3 square pyramids, corners with two equivalent S(1)Pr3Er2 trigonal bipyramids, corners with two equivalent S(8)Pr3Er2 trigonal bipyramids,  an edgeedge with one S(7)Pr2Er3 square pyramid, edges with two equivalent S(6)Pr2Er3 square pyramids,  an edgeedge with one S(8)Pr3Er2 trigonal bipyramid, edges with two equivalent S(5)Pr2Er3 trigonal bipyramids, and edges with two equivalent S(9)PrEr3 trigonal pyramids. In the seventh S site, S(7) is bonded to one Er(2), two equivalent Er(6), and two equivalent Pr(1) atoms to form SPr2Er3 square pyramids that share corners with two equivalent S(6)Pr2Er3 square pyramids, corners with two equivalent S(7)Pr2Er3 square pyramids, corners with two equivalent S(8)Pr3Er2 trigonal bipyramids, corners with two equivalent S(9)PrEr3 trigonal pyramids,  an edgeedge with one S(6)Pr2Er3 square pyramid, edges with three equivalent S(7)Pr2Er3 square pyramids,  an edgeedge with one S(8)Pr3Er2 trigonal bipyramid, and edges with two equivalent S(1)Pr3Er2 trigonal bipyramids. In the eighth S site, S(8) is bonded to two equivalent Er(1), one Pr(2), and two equivalent Pr(1) atoms to form distorted SPr3Er2 trigonal bipyramids that share corners with two equivalent S(6)Pr2Er3 square pyramids, corners with two equivalent S(7)Pr2Er3 square pyramids, corners with two equivalent S(5)Pr2Er3 trigonal bipyramids, corners with four equivalent S(11)Er4 trigonal pyramids,  an edgeedge with one S(6)Pr2Er3 square pyramid,  an edgeedge with one S(7)Pr2Er3 square pyramid, edges with two equivalent S(2)Pr2Er3 trigonal bipyramids, edges with two equivalent S(1)Pr3Er2 trigonal bipyramids, edges with two equivalent S(8)Pr3Er2 trigonal bipyramids,  an edgeedge with one S(11)Er4 trigonal pyramid, and edges with two equivalent S(9)PrEr3 trigonal pyramids. In the ninth S site, S(9) is bonded to one Er(1), two equivalent Er(3), and one Pr(1) atom to form SPrEr3 trigonal pyramids that share corners with two equivalent S(7)Pr2Er3 square pyramids,  a cornercorner with one S(2)Pr2Er3 trigonal bipyramid,  a cornercorner with one S(1)Pr3Er2 trigonal bipyramid, corners with two equivalent S(5)Pr2Er3 trigonal bipyramids, corners with two equivalent S(9)PrEr3 trigonal pyramids, corners with three equivalent S(11)Er4 trigonal pyramids, edges with two equivalent S(6)Pr2Er3 square pyramids,  an edgeedge with one S(5)Pr2Er3 trigonal bipyramid, and edges with two equivalent S(8)Pr3Er2 trigonal bipyramids. In the tenth S site, S(10) is bonded in a rectangular see-saw-like geometry to one Er(5), one Er(6), and two equivalent Er(2) atoms. In the eleventh S site, S(11) is bonded to one Er(4) and three equivalent Er(1) atoms to form distorted SEr4 trigonal pyramids that share  a cornercorner with one S(2)Pr2Er3 trigonal bipyramid, corners with four equivalent S(8)Pr3Er2 trigonal bipyramids, corners with two equivalent S(11)Er4 trigonal pyramids, corners with three equivalent S(9)PrEr3 trigonal pyramids,  an edgeedge with one S(8)Pr3Er2 trigonal bipyramid, edges with two equivalent S(2)Pr2Er3 trigonal bipyramids, and edges with two equivalent S(11)Er4 trigonal pyramids.
Pr4(ErS2)11 crystallizes in the monoclinic C2/m space group. There are six inequivalent Er sites. In the first Er site, Er(1) is bonded to one S(2), one S(9), two equivalent S(8), and three equivalent S(11) atoms to form distorted ErS7 pentagonal bipyramids that share  a cornercorner with one Er(4)S6 octahedra, corners with two equivalent Er(3)S6 octahedra, edges with two equivalent Er(4)S6 octahedra, and edges with four equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 39-50°. The Er(1)-S(2) bond length is 2.87 Å. The Er(1)-S(9) bond length is 2.75 Å. Both Er(1)-S(8) bond lengths are 2.87 Å. There are two shorter (2.69 Å) and one longer (2.86 Å) Er(1)-S(11) bond length. In the second Er site, Er(2) is bonded to one S(4), one S(7), two equivalent S(1), and two equivalent S(10) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles range from 49-59°. The Er(2)-S(4) bond length is 2.64 Å. The Er(2)-S(7) bond length is 2.74 Å. Both Er(2)-S(1) bond lengths are 2.76 Å. Both Er(2)-S(10) bond lengths are 2.70 Å. In the third Er site, Er(3) is bonded to one S(3), one S(6), two equivalent S(5), and two equivalent S(9) atoms to form ErS6 octahedra that share corners with three equivalent Er(4)S6 octahedra, corners with two equivalent Er(1)S7 pentagonal bipyramids, edges with two equivalent Er(3)S6 octahedra, and edges with two equivalent Er(5)S6 octahedra. The corner-sharing octahedral tilt angles range from 51-62°. The Er(3)-S(3) bond length is 2.71 Å. The Er(3)-S(6) bond length is 2.71 Å. Both Er(3)-S(5) bond lengths are 2.79 Å. Both Er(3)-S(9) bond lengths are 2.65 Å. In the fourth Er site, Er(4) is bonded to one S(11), two equivalent S(2), and three equivalent S(3) atoms to form ErS6 octahedra that share corners with three equivalent Er(3)S6 octahedra,  a cornercorner with one Er(1)S7 pentagonal bipyramid, edges with four equivalent Er(4)S6 octahedra, and edges with two equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 51-62°. The Er(4)-S(11) bond length is 2.66 Å. Both Er(4)-S(2) bond lengths are 2.76 Å. There are two shorter (2.72 Å) and one longer (2.76 Å) Er(4)-S(3) bond length. In the fifth Er site, Er(5) is bonded to one S(10), one S(5), two equivalent S(4), and two equivalent S(6) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles range from 49-59°. The Er(5)-S(10) bond length is 2.75 Å. The Er(5)-S(5) bond length is 2.74 Å. Both Er(5)-S(4) bond lengths are 2.65 Å. Both Er(5)-S(6) bond lengths are 2.76 Å. In the sixth Er site, Er(6) is bonded to two equivalent S(10) and four equivalent S(7) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles are 55°. Both Er(6)-S(10) bond lengths are 2.72 Å. All Er(6)-S(7) bond lengths are 2.72 Å. There are two inequivalent Pr sites. In the first Pr site, Pr(1) is bonded in a 8-coordinate geometry to one S(1), one S(9), two equivalent S(6), two equivalent S(7), and two equivalent S(8) atoms. The Pr(1)-S(1) bond length is 3.01 Å. The Pr(1)-S(9) bond length is 2.94 Å. Both Pr(1)-S(6) bond lengths are 3.05 Å. Both Pr(1)-S(7) bond lengths are 3.02 Å. Both Pr(1)-S(8) bond lengths are 2.92 Å. In the second Pr site, Pr(2) is bonded in a 8-coordinate geometry to one S(4), one S(8), two equivalent S(1), two equivalent S(2), and two equivalent S(5) atoms. The Pr(2)-S(4) bond length is 3.47 Å. The Pr(2)-S(8) bond length is 2.96 Å. Both Pr(2)-S(1) bond lengths are 2.91 Å. Both Pr(2)-S(2) bond lengths are 2.98 Å. Both Pr(2)-S(5) bond lengths are 3.00 Å. There are eleven inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Er(2), one Pr(1), and two equivalent Pr(2) atoms to form distorted SPr3Er2 trigonal bipyramids that share corners with two equivalent S(6)Pr2Er3 square pyramids, corners with two equivalent S(2)Pr2Er3 trigonal bipyramids, corners with two equivalent S(5)Pr2Er3 trigonal bipyramids,  a cornercorner with one S(9)PrEr3 trigonal pyramid, edges with two equivalent S(7)Pr2Er3 square pyramids,  an edgeedge with one S(2)Pr2Er3 trigonal bipyramid,  an edgeedge with one S(5)Pr2Er3 trigonal bipyramid, edges with two equivalent S(1)Pr3Er2 trigonal bipyramids, and edges with two equivalent S(8)Pr3Er2 trigonal bipyramids. In the second S site, S(2) is bonded to one Er(1), two equivalent Er(4), and two equivalent Pr(2) atoms to form SPr2Er3 trigonal bipyramids that share corners with two equivalent S(5)Pr2Er3 trigonal bipyramids, corners with two equivalent S(1)Pr3Er2 trigonal bipyramids,  a cornercorner with one S(11)Er4 trigonal pyramid,  a cornercorner with one S(9)PrEr3 trigonal pyramid,  an edgeedge with one S(5)Pr2Er3 trigonal bipyramid,  an edgeedge with one S(1)Pr3Er2 trigonal bipyramid, edges with two equivalent S(2)Pr2Er3 trigonal bipyramids, edges with two equivalent S(8)Pr3Er2 trigonal bipyramids, and edges with two equivalent S(11)Er4 trigonal pyramids. In the third S site, S(3) is bonded in a rectangular see-saw-like geometry to one Er(3) and three equivalent Er(4) atoms. In the fourth S site, S(4) is bonded in a 3-coordinate geometry to one Er(2), two equivalent Er(5), and one Pr(2) atom. In the fifth S site, S(5) is bonded to one Er(5), two equivalent Er(3), and two equivalent Pr(2) atoms to form SPr2Er3 trigonal bipyramids that share corners with two equivalent S(2)Pr2Er3 trigonal bipyramids, corners with two equivalent S(1)Pr3Er2 trigonal bipyramids, corners with two equivalent S(8)Pr3Er2 trigonal bipyramids, corners with two equivalent S(9)PrEr3 trigonal pyramids, edges with two equivalent S(6)Pr2Er3 square pyramids,  an edgeedge with one S(2)Pr2Er3 trigonal bipyramid,  an edgeedge with one S(1)Pr3Er2 trigonal bipyramid, edges with two equivalent S(5)Pr2Er3 trigonal bipyramids, and  an edgeedge with one S(9)PrEr3 trigonal pyramid. In the sixth S site, S(6) is bonded to one Er(3), two equivalent Er(5), and two equivalent Pr(1) atoms to form SPr2Er3 square pyramids that share corners with two equivalent S(7)Pr2Er3 square pyramids, corners with two equivalent S(1)Pr3Er2 trigonal bipyramids, corners with two equivalent S(8)Pr3Er2 trigonal bipyramids,  an edgeedge with one S(7)Pr2Er3 square pyramid, edges with two equivalent S(6)Pr2Er3 square pyramids,  an edgeedge with one S(8)Pr3Er2 trigonal bipyramid, edges with two equivalent S(5)Pr2Er3 trigonal bipyramids, and edges with two equivalent S(9)PrEr3 trigonal pyramids. In the seventh S site, S(7) is bonded to one Er(2), two equivalent Er(6), and two equivalent Pr(1) atoms to form SPr2Er3 square pyramids that share corners with two equivalent S(6)Pr2Er3 square pyramids, corners with two equivalent S(7)Pr2Er3 square pyramids, corners with two equivalent S(8)Pr3Er2 trigonal bipyramids, corners with two equivalent S(9)PrEr3 trigonal pyramids,  an edgeedge with one S(6)Pr2Er3 square pyramid, edges with three equivalent S(7)Pr2Er3 square pyramids,  an edgeedge with one S(8)Pr3Er2 trigonal bipyramid, and edges with two equivalent S(1)Pr3Er2 trigonal bipyramids. In the eighth S site, S(8) is bonded to two equivalent Er(1), one Pr(2), and two equivalent Pr(1) atoms to form distorted SPr3Er2 trigonal bipyramids that share corners with two equivalent S(6)Pr2Er3 square pyramids, corners with two equivalent S(7)Pr2Er3 square pyramids, corners with two equivalent S(5)Pr2Er3 trigonal bipyramids, corners with four equivalent S(11)Er4 trigonal pyramids,  an edgeedge with one S(6)Pr2Er3 square pyramid,  an edgeedge with one S(7)Pr2Er3 square pyramid, edges with two equivalent S(2)Pr2Er3 trigonal bipyramids, edges with two equivalent S(1)Pr3Er2 trigonal bipyramids, edges with two equivalent S(8)Pr3Er2 trigonal bipyramids,  an edgeedge with one S(11)Er4 trigonal pyramid, and edges with two equivalent S(9)PrEr3 trigonal pyramids. In the ninth S site, S(9) is bonded to one Er(1), two equivalent Er(3), and one Pr(1) atom to form SPrEr3 trigonal pyramids that share corners with two equivalent S(7)Pr2Er3 square pyramids,  a cornercorner with one S(2)Pr2Er3 trigonal bipyramid,  a cornercorner with one S(1)Pr3Er2 trigonal bipyramid, corners with two equivalent S(5)Pr2Er3 trigonal bipyramids, corners with two equivalent S(9)PrEr3 trigonal pyramids, corners with three equivalent S(11)Er4 trigonal pyramids, edges with two equivalent S(6)Pr2Er3 square pyramids,  an edgeedge with one S(5)Pr2Er3 trigonal bipyramid, and edges with two equivalent S(8)Pr3Er2 trigonal bipyramids. In the tenth S site, S(10) is bonded in a rectangular see-saw-like geometry to one Er(5), one Er(6), and two equivalent Er(2) atoms. In the eleventh S site, S(11) is bonded to one Er(4) and three equivalent Er(1) atoms to form distorted SEr4 trigonal pyramids that share  a cornercorner with one S(2)Pr2Er3 trigonal bipyramid, corners with four equivalent S(8)Pr3Er2 trigonal bipyramids, corners with two equivalent S(11)Er4 trigonal pyramids, corners with three equivalent S(9)PrEr3 trigonal pyramids,  an edgeedge with one S(8)Pr3Er2 trigonal bipyramid, edges with two equivalent S(2)Pr2Er3 trigonal bipyramids, and edges with two equivalent S(11)Er4 trigonal pyramids.