Nb3(CuSe3)2 crystallizes in the monoclinic P2_1 space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one Se(2), one Se(6), two equivalent Se(1), and two equivalent Se(4) atoms. In the second Nb site, Nb(2) is bonded to one Se(1), one Se(4), two equivalent Se(3), and two equivalent Se(5) atoms to form distorted edge-sharing NbSe6 pentagonal pyramids. In the third Nb site, Nb(3) is bonded in a 6-coordinate geometry to one Se(3), one Se(5), two equivalent Se(2), and two equivalent Se(6) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 4-coordinate geometry to one Se(2), one Se(4), and two equivalent Se(1) atoms. In the second Cu site, Cu(2) is bonded in a 4-coordinate geometry to one Se(3), one Se(5), and two equivalent Se(6) atoms. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded to one Nb(2), two equivalent Nb(1), and two equivalent Cu(1) atoms to form distorted edge-sharing SeNb3Cu2 square pyramids. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Nb(1), two equivalent Nb(3), and one Cu(1) atom. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Nb(3), two equivalent Nb(2), and one Cu(2) atom. In the fourth Se site, Se(4) is bonded in a rectangular see-saw-like geometry to one Nb(2), two equivalent Nb(1), and one Cu(1) atom. In the fifth Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one Nb(3), two equivalent Nb(2), and one Cu(2) atom. In the sixth Se site, Se(6) is bonded in a 5-coordinate geometry to one Nb(1), two equivalent Nb(3), and two equivalent Cu(2) atoms.
Nb3(CuSe3)2 crystallizes in the monoclinic P2_1 space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one Se(2), one Se(6), two equivalent Se(1), and two equivalent Se(4) atoms. The Nb(1)-Se(2) bond length is 2.66 Å. The Nb(1)-Se(6) bond length is 2.60 Å. There is one shorter (2.66 Å) and one longer (2.67 Å) Nb(1)-Se(1) bond length. Both Nb(1)-Se(4) bond lengths are 2.62 Å. In the second Nb site, Nb(2) is bonded to one Se(1), one Se(4), two equivalent Se(3), and two equivalent Se(5) atoms to form distorted edge-sharing NbSe6 pentagonal pyramids. The Nb(2)-Se(1) bond length is 2.62 Å. The Nb(2)-Se(4) bond length is 2.61 Å. There is one shorter (2.60 Å) and one longer (2.61 Å) Nb(2)-Se(3) bond length. Both Nb(2)-Se(5) bond lengths are 2.61 Å. In the third Nb site, Nb(3) is bonded in a 6-coordinate geometry to one Se(3), one Se(5), two equivalent Se(2), and two equivalent Se(6) atoms. The Nb(3)-Se(3) bond length is 2.61 Å. The Nb(3)-Se(5) bond length is 2.68 Å. There is one shorter (2.61 Å) and one longer (2.62 Å) Nb(3)-Se(2) bond length. Both Nb(3)-Se(6) bond lengths are 2.67 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 4-coordinate geometry to one Se(2), one Se(4), and two equivalent Se(1) atoms. The Cu(1)-Se(2) bond length is 2.40 Å. The Cu(1)-Se(4) bond length is 2.33 Å. There is one shorter (2.41 Å) and one longer (2.42 Å) Cu(1)-Se(1) bond length. In the second Cu site, Cu(2) is bonded in a 4-coordinate geometry to one Se(3), one Se(5), and two equivalent Se(6) atoms. The Cu(2)-Se(3) bond length is 2.31 Å. The Cu(2)-Se(5) bond length is 2.38 Å. There is one shorter (2.41 Å) and one longer (2.42 Å) Cu(2)-Se(6) bond length. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded to one Nb(2), two equivalent Nb(1), and two equivalent Cu(1) atoms to form distorted edge-sharing SeNb3Cu2 square pyramids. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Nb(1), two equivalent Nb(3), and one Cu(1) atom. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Nb(3), two equivalent Nb(2), and one Cu(2) atom. In the fourth Se site, Se(4) is bonded in a rectangular see-saw-like geometry to one Nb(2), two equivalent Nb(1), and one Cu(1) atom. In the fifth Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one Nb(3), two equivalent Nb(2), and one Cu(2) atom. In the sixth Se site, Se(6) is bonded in a 5-coordinate geometry to one Nb(1), two equivalent Nb(3), and two equivalent Cu(2) atoms.