Eu2(ZrSe2)5 crystallizes in the triclinic P-1 space group. Eu(1) is bonded to one Se(1), one Se(2), one Se(4), one Se(5), and two equivalent Se(3) atoms to form distorted EuSe6 octahedra that share corners with three equivalent Zr(1)Se6 octahedra, corners with four equivalent Zr(2)Se6 octahedra, corners with five equivalent Zr(3)Se6 octahedra,  an edgeedge with one Eu(1)Se6 octahedra,  a faceface with one Zr(2)Se6 octahedra, and  a faceface with one Zr(3)Se6 octahedra. The corner-sharing octahedral tilt angles range from 44-49°. There are three inequivalent Zr sites. In the first Zr site, Zr(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(5) atoms to form ZrSe6 octahedra that share corners with six equivalent Eu(1)Se6 octahedra, edges with two equivalent Zr(3)Se6 octahedra, and edges with four equivalent Zr(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 44-48°. In the second Zr site, Zr(2) is bonded to one Se(2), one Se(3), one Se(4), one Se(5), and two equivalent Se(1) atoms to form ZrSe6 octahedra that share corners with four equivalent Eu(1)Se6 octahedra,  an edgeedge with one Zr(2)Se6 octahedra, edges with two equivalent Zr(1)Se6 octahedra, edges with three equivalent Zr(3)Se6 octahedra, and  a faceface with one Eu(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 44-49°. In the third Zr site, Zr(3) is bonded to one Se(2), one Se(5), two equivalent Se(3), and two equivalent Se(4) atoms to form ZrSe6 octahedra that share corners with five equivalent Eu(1)Se6 octahedra,  an edgeedge with one Zr(1)Se6 octahedra, edges with two equivalent Zr(3)Se6 octahedra, edges with three equivalent Zr(2)Se6 octahedra, and  a faceface with one Eu(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 44-47°. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded in a rectangular see-saw-like geometry to one Eu(1), one Zr(1), and two equivalent Zr(2) atoms. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Eu(1), one Zr(1), one Zr(2), and one Zr(3) atom. In the third Se site, Se(3) is bonded to two equivalent Eu(1), one Zr(2), and two equivalent Zr(3) atoms to form distorted edge-sharing SeEu2Zr3 trigonal bipyramids. In the fourth Se site, Se(4) is bonded in a rectangular see-saw-like geometry to one Eu(1), one Zr(2), and two equivalent Zr(3) atoms. In the fifth Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one Eu(1), one Zr(1), one Zr(2), and one Zr(3) atom.
Eu2(ZrSe2)5 crystallizes in the triclinic P-1 space group. Eu(1) is bonded to one Se(1), one Se(2), one Se(4), one Se(5), and two equivalent Se(3) atoms to form distorted EuSe6 octahedra that share corners with three equivalent Zr(1)Se6 octahedra, corners with four equivalent Zr(2)Se6 octahedra, corners with five equivalent Zr(3)Se6 octahedra,  an edgeedge with one Eu(1)Se6 octahedra,  a faceface with one Zr(2)Se6 octahedra, and  a faceface with one Zr(3)Se6 octahedra. The corner-sharing octahedral tilt angles range from 44-49°. The Eu(1)-Se(1) bond length is 2.97 Å. The Eu(1)-Se(2) bond length is 3.02 Å. The Eu(1)-Se(4) bond length is 3.02 Å. The Eu(1)-Se(5) bond length is 2.97 Å. Both Eu(1)-Se(3) bond lengths are 3.08 Å. There are three inequivalent Zr sites. In the first Zr site, Zr(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(5) atoms to form ZrSe6 octahedra that share corners with six equivalent Eu(1)Se6 octahedra, edges with two equivalent Zr(3)Se6 octahedra, and edges with four equivalent Zr(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 44-48°. Both Zr(1)-Se(1) bond lengths are 2.72 Å. Both Zr(1)-Se(2) bond lengths are 2.73 Å. Both Zr(1)-Se(5) bond lengths are 2.71 Å. In the second Zr site, Zr(2) is bonded to one Se(2), one Se(3), one Se(4), one Se(5), and two equivalent Se(1) atoms to form ZrSe6 octahedra that share corners with four equivalent Eu(1)Se6 octahedra,  an edgeedge with one Zr(2)Se6 octahedra, edges with two equivalent Zr(1)Se6 octahedra, edges with three equivalent Zr(3)Se6 octahedra, and  a faceface with one Eu(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 44-49°. The Zr(2)-Se(2) bond length is 2.75 Å. The Zr(2)-Se(3) bond length is 2.78 Å. The Zr(2)-Se(4) bond length is 2.74 Å. The Zr(2)-Se(5) bond length is 2.72 Å. There is one shorter (2.71 Å) and one longer (2.77 Å) Zr(2)-Se(1) bond length. In the third Zr site, Zr(3) is bonded to one Se(2), one Se(5), two equivalent Se(3), and two equivalent Se(4) atoms to form ZrSe6 octahedra that share corners with five equivalent Eu(1)Se6 octahedra,  an edgeedge with one Zr(1)Se6 octahedra, edges with two equivalent Zr(3)Se6 octahedra, edges with three equivalent Zr(2)Se6 octahedra, and  a faceface with one Eu(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 44-47°. The Zr(3)-Se(2) bond length is 2.70 Å. The Zr(3)-Se(5) bond length is 2.79 Å. There is one shorter (2.77 Å) and one longer (2.78 Å) Zr(3)-Se(3) bond length. There is one shorter (2.72 Å) and one longer (2.73 Å) Zr(3)-Se(4) bond length. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded in a rectangular see-saw-like geometry to one Eu(1), one Zr(1), and two equivalent Zr(2) atoms. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Eu(1), one Zr(1), one Zr(2), and one Zr(3) atom. In the third Se site, Se(3) is bonded to two equivalent Eu(1), one Zr(2), and two equivalent Zr(3) atoms to form distorted edge-sharing SeEu2Zr3 trigonal bipyramids. In the fourth Se site, Se(4) is bonded in a rectangular see-saw-like geometry to one Eu(1), one Zr(2), and two equivalent Zr(3) atoms. In the fifth Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one Eu(1), one Zr(1), one Zr(2), and one Zr(3) atom.