IrSe3 crystallizes in the triclinic P1 space group. There are seven inequivalent Ir sites. In the first Ir site, Ir(1) is bonded to one Se(1), one Se(10), one Se(12), one Se(16), one Se(4), and one Se(6) atom to form IrSe6 octahedra that share corners with two equivalent Ir(2)Se6 octahedra, corners with two equivalent Ir(7)Se6 octahedra, corners with two equivalent Ir(6)Se5 square pyramids, and  a cornercorner with one Se(8)Ir3Se tetrahedra. The corner-sharing octahedral tilt angles range from 63-67°. In the second Ir site, Ir(2) is bonded to one Se(10), one Se(14), one Se(17), one Se(2), one Se(4), and one Se(8) atom to form IrSe6 octahedra that share corners with two equivalent Ir(1)Se6 octahedra, corners with two equivalent Ir(3)Se6 octahedra, corners with four equivalent Ir(7)Se6 octahedra,  a cornercorner with one Se(10)Ir3Se tetrahedra, and  a cornercorner with one Se(8)Ir3Se tetrahedra. The corner-sharing octahedral tilt angles range from 63-66°. In the third Ir site, Ir(3) is bonded to one Se(11), one Se(14), one Se(18), one Se(3), one Se(5), and one Se(8) atom to form IrSe6 octahedra that share corners with two equivalent Ir(2)Se6 octahedra, corners with two equivalent Ir(7)Se6 octahedra,  a cornercorner with one Se(10)Ir3Se tetrahedra, and corners with two equivalent Ir(4)Se5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 63-67°. In the fourth Ir site, Ir(4) is bonded to one Se(11), one Se(15), one Se(19), one Se(5), and one Se(9) atom to form IrSe5 trigonal bipyramids that share corners with two equivalent Ir(3)Se6 octahedra and corners with two equivalent Ir(5)Se5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 60-63°. In the fifth Ir site, Ir(5) is bonded to one Se(13), one Se(15), one Se(20), one Se(7), and one Se(9) atom to form corner-sharing IrSe5 trigonal bipyramids. In the sixth Ir site, Ir(6) is bonded to one Se(12), one Se(13), one Se(21), one Se(6), and one Se(7) atom to form IrSe5 square pyramids that share corners with two equivalent Ir(1)Se6 octahedra and corners with two equivalent Ir(5)Se5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 60-63°. In the seventh Ir site, Ir(7) is bonded to one Se(1), one Se(10), one Se(17), one Se(18), one Se(2), and one Se(8) atom to form IrSe6 octahedra that share corners with two equivalent Ir(1)Se6 octahedra, corners with two equivalent Ir(3)Se6 octahedra, corners with four equivalent Ir(2)Se6 octahedra,  a cornercorner with one Se(10)Ir3Se tetrahedra, and  a cornercorner with one Se(8)Ir3Se tetrahedra. The corner-sharing octahedral tilt angles range from 63-67°. There are twenty-one inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted trigonal non-coplanar geometry to one Ir(1), one Ir(7), and one Se(16) atom. In the second Se site, Se(2) is bonded in a distorted trigonal non-coplanar geometry to one Ir(2), one Ir(7), and one Se(17) atom. In the third Se site, Se(3) is bonded in a water-like geometry to one Ir(3) and one Se(18) atom. In the fourth Se site, Se(4) is bonded in a distorted trigonal non-coplanar geometry to one Ir(1), one Ir(2), and one Se(12) atom. In the fifth Se site, Se(5) is bonded in a distorted trigonal non-coplanar geometry to one Ir(3), one Ir(4), and one Se(14) atom. In the sixth Se site, Se(6) is bonded in a 3-coordinate geometry to one Ir(1), one Ir(6), and one Se(13) atom. In the seventh Se site, Se(7) is bonded in a 2-coordinate geometry to one Ir(5), one Ir(6), and one Se(15) atom. In the eighth Se site, Se(8) is bonded to one Ir(2), one Ir(3), one Ir(7), and one Se(10) atom to form distorted SeIr3Se tetrahedra that share  a cornercorner with one Ir(1)Se6 octahedra,  a cornercorner with one Ir(2)Se6 octahedra,  a cornercorner with one Ir(7)Se6 octahedra, and corners with two equivalent Se(10)Ir3Se tetrahedra. The corner-sharing octahedral tilt angles range from 78-80°. In the ninth Se site, Se(9) is bonded in a distorted trigonal non-coplanar geometry to one Ir(4), one Ir(5), and one Se(11) atom. In the tenth Se site, Se(10) is bonded to one Ir(1), one Ir(2), one Ir(7), and one Se(8) atom to form distorted SeIr3Se tetrahedra that share  a cornercorner with one Ir(2)Se6 octahedra,  a cornercorner with one Ir(3)Se6 octahedra,  a cornercorner with one Ir(7)Se6 octahedra, and corners with two equivalent Se(8)Ir3Se tetrahedra. The corner-sharing octahedral tilt angles range from 79-81°. In the eleventh Se site, Se(11) is bonded in a distorted trigonal non-coplanar geometry to one Ir(3), one Ir(4), and one Se(9) atom. In the twelfth Se site, Se(12) is bonded in a distorted trigonal non-coplanar geometry to one Ir(1), one Ir(6), and one Se(4) atom. In the thirteenth Se site, Se(13) is bonded in a distorted trigonal non-coplanar geometry to one Ir(5), one Ir(6), and one Se(6) atom. In the fourteenth Se site, Se(14) is bonded in a distorted trigonal non-coplanar geometry to one Ir(2), one Ir(3), and one Se(5) atom. In the fifteenth Se site, Se(15) is bonded in a distorted trigonal planar geometry to one Ir(4), one Ir(5), and one Se(7) atom. In the sixteenth Se site, Se(16) is bonded in a water-like geometry to one Ir(1) and one Se(1) atom. In the seventeenth Se site, Se(17) is bonded in a distorted trigonal non-coplanar geometry to one Ir(2), one Ir(7), and one Se(2) atom. In the eighteenth Se site, Se(18) is bonded in a trigonal non-coplanar geometry to one Ir(3), one Ir(7), and one Se(3) atom. In the nineteenth Se site, Se(19) is bonded in a distorted water-like geometry to one Ir(4) and one Se(20) atom. In the twentieth Se site, Se(20) is bonded in a distorted trigonal non-coplanar geometry to one Ir(5), one Se(19), and one Se(21) atom. In the twenty-first Se site, Se(21) is bonded in a distorted single-bond geometry to one Ir(6) and one Se(20) atom.
IrSe3 crystallizes in the triclinic P1 space group. There are seven inequivalent Ir sites. In the first Ir site, Ir(1) is bonded to one Se(1), one Se(10), one Se(12), one Se(16), one Se(4), and one Se(6) atom to form IrSe6 octahedra that share corners with two equivalent Ir(2)Se6 octahedra, corners with two equivalent Ir(7)Se6 octahedra, corners with two equivalent Ir(6)Se5 square pyramids, and  a cornercorner with one Se(8)Ir3Se tetrahedra. The corner-sharing octahedral tilt angles range from 63-67°. The Ir(1)-Se(1) bond length is 2.54 Å. The Ir(1)-Se(10) bond length is 2.50 Å. The Ir(1)-Se(12) bond length is 2.52 Å. The Ir(1)-Se(16) bond length is 2.50 Å. The Ir(1)-Se(4) bond length is 2.51 Å. The Ir(1)-Se(6) bond length is 2.48 Å. In the second Ir site, Ir(2) is bonded to one Se(10), one Se(14), one Se(17), one Se(2), one Se(4), and one Se(8) atom to form IrSe6 octahedra that share corners with two equivalent Ir(1)Se6 octahedra, corners with two equivalent Ir(3)Se6 octahedra, corners with four equivalent Ir(7)Se6 octahedra,  a cornercorner with one Se(10)Ir3Se tetrahedra, and  a cornercorner with one Se(8)Ir3Se tetrahedra. The corner-sharing octahedral tilt angles range from 63-66°. The Ir(2)-Se(10) bond length is 2.50 Å. The Ir(2)-Se(14) bond length is 2.50 Å. The Ir(2)-Se(17) bond length is 2.56 Å. The Ir(2)-Se(2) bond length is 2.55 Å. The Ir(2)-Se(4) bond length is 2.51 Å. The Ir(2)-Se(8) bond length is 2.51 Å. In the third Ir site, Ir(3) is bonded to one Se(11), one Se(14), one Se(18), one Se(3), one Se(5), and one Se(8) atom to form IrSe6 octahedra that share corners with two equivalent Ir(2)Se6 octahedra, corners with two equivalent Ir(7)Se6 octahedra,  a cornercorner with one Se(10)Ir3Se tetrahedra, and corners with two equivalent Ir(4)Se5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 63-67°. The Ir(3)-Se(11) bond length is 2.49 Å. The Ir(3)-Se(14) bond length is 2.50 Å. The Ir(3)-Se(18) bond length is 2.54 Å. The Ir(3)-Se(3) bond length is 2.50 Å. The Ir(3)-Se(5) bond length is 2.52 Å. The Ir(3)-Se(8) bond length is 2.52 Å. In the fourth Ir site, Ir(4) is bonded to one Se(11), one Se(15), one Se(19), one Se(5), and one Se(9) atom to form IrSe5 trigonal bipyramids that share corners with two equivalent Ir(3)Se6 octahedra and corners with two equivalent Ir(5)Se5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 60-63°. The Ir(4)-Se(11) bond length is 2.49 Å. The Ir(4)-Se(15) bond length is 2.43 Å. The Ir(4)-Se(19) bond length is 2.44 Å. The Ir(4)-Se(5) bond length is 2.44 Å. The Ir(4)-Se(9) bond length is 2.46 Å. In the fifth Ir site, Ir(5) is bonded to one Se(13), one Se(15), one Se(20), one Se(7), and one Se(9) atom to form corner-sharing IrSe5 trigonal bipyramids. The Ir(5)-Se(13) bond length is 2.52 Å. The Ir(5)-Se(15) bond length is 2.36 Å. The Ir(5)-Se(20) bond length is 2.39 Å. The Ir(5)-Se(7) bond length is 2.48 Å. The Ir(5)-Se(9) bond length is 2.46 Å. In the sixth Ir site, Ir(6) is bonded to one Se(12), one Se(13), one Se(21), one Se(6), and one Se(7) atom to form IrSe5 square pyramids that share corners with two equivalent Ir(1)Se6 octahedra and corners with two equivalent Ir(5)Se5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 60-63°. The Ir(6)-Se(12) bond length is 2.47 Å. The Ir(6)-Se(13) bond length is 2.49 Å. The Ir(6)-Se(21) bond length is 2.46 Å. The Ir(6)-Se(6) bond length is 2.49 Å. The Ir(6)-Se(7) bond length is 2.42 Å. In the seventh Ir site, Ir(7) is bonded to one Se(1), one Se(10), one Se(17), one Se(18), one Se(2), and one Se(8) atom to form IrSe6 octahedra that share corners with two equivalent Ir(1)Se6 octahedra, corners with two equivalent Ir(3)Se6 octahedra, corners with four equivalent Ir(2)Se6 octahedra,  a cornercorner with one Se(10)Ir3Se tetrahedra, and  a cornercorner with one Se(8)Ir3Se tetrahedra. The corner-sharing octahedral tilt angles range from 63-67°. The Ir(7)-Se(1) bond length is 2.55 Å. The Ir(7)-Se(10) bond length is 2.51 Å. The Ir(7)-Se(17) bond length is 2.51 Å. The Ir(7)-Se(18) bond length is 2.55 Å. The Ir(7)-Se(2) bond length is 2.51 Å. The Ir(7)-Se(8) bond length is 2.51 Å. There are twenty-one inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted trigonal non-coplanar geometry to one Ir(1), one Ir(7), and one Se(16) atom. The Se(1)-Se(16) bond length is 2.40 Å. In the second Se site, Se(2) is bonded in a distorted trigonal non-coplanar geometry to one Ir(2), one Ir(7), and one Se(17) atom. The Se(2)-Se(17) bond length is 2.50 Å. In the third Se site, Se(3) is bonded in a water-like geometry to one Ir(3) and one Se(18) atom. The Se(3)-Se(18) bond length is 2.40 Å. In the fourth Se site, Se(4) is bonded in a distorted trigonal non-coplanar geometry to one Ir(1), one Ir(2), and one Se(12) atom. The Se(4)-Se(12) bond length is 2.47 Å. In the fifth Se site, Se(5) is bonded in a distorted trigonal non-coplanar geometry to one Ir(3), one Ir(4), and one Se(14) atom. The Se(5)-Se(14) bond length is 2.46 Å. In the sixth Se site, Se(6) is bonded in a 3-coordinate geometry to one Ir(1), one Ir(6), and one Se(13) atom. The Se(6)-Se(13) bond length is 2.48 Å. In the seventh Se site, Se(7) is bonded in a 2-coordinate geometry to one Ir(5), one Ir(6), and one Se(15) atom. The Se(7)-Se(15) bond length is 2.53 Å. In the eighth Se site, Se(8) is bonded to one Ir(2), one Ir(3), one Ir(7), and one Se(10) atom to form distorted SeIr3Se tetrahedra that share  a cornercorner with one Ir(1)Se6 octahedra,  a cornercorner with one Ir(2)Se6 octahedra,  a cornercorner with one Ir(7)Se6 octahedra, and corners with two equivalent Se(10)Ir3Se tetrahedra. The corner-sharing octahedral tilt angles range from 78-80°. The Se(8)-Se(10) bond length is 2.53 Å. In the ninth Se site, Se(9) is bonded in a distorted trigonal non-coplanar geometry to one Ir(4), one Ir(5), and one Se(11) atom. The Se(9)-Se(11) bond length is 2.54 Å. In the tenth Se site, Se(10) is bonded to one Ir(1), one Ir(2), one Ir(7), and one Se(8) atom to form distorted SeIr3Se tetrahedra that share  a cornercorner with one Ir(2)Se6 octahedra,  a cornercorner with one Ir(3)Se6 octahedra,  a cornercorner with one Ir(7)Se6 octahedra, and corners with two equivalent Se(8)Ir3Se tetrahedra. The corner-sharing octahedral tilt angles range from 79-81°. In the eleventh Se site, Se(11) is bonded in a distorted trigonal non-coplanar geometry to one Ir(3), one Ir(4), and one Se(9) atom. In the twelfth Se site, Se(12) is bonded in a distorted trigonal non-coplanar geometry to one Ir(1), one Ir(6), and one Se(4) atom. In the thirteenth Se site, Se(13) is bonded in a distorted trigonal non-coplanar geometry to one Ir(5), one Ir(6), and one Se(6) atom. In the fourteenth Se site, Se(14) is bonded in a distorted trigonal non-coplanar geometry to one Ir(2), one Ir(3), and one Se(5) atom. In the fifteenth Se site, Se(15) is bonded in a distorted trigonal planar geometry to one Ir(4), one Ir(5), and one Se(7) atom. In the sixteenth Se site, Se(16) is bonded in a water-like geometry to one Ir(1) and one Se(1) atom. In the seventeenth Se site, Se(17) is bonded in a distorted trigonal non-coplanar geometry to one Ir(2), one Ir(7), and one Se(2) atom. In the eighteenth Se site, Se(18) is bonded in a trigonal non-coplanar geometry to one Ir(3), one Ir(7), and one Se(3) atom. In the nineteenth Se site, Se(19) is bonded in a distorted water-like geometry to one Ir(4) and one Se(20) atom. The Se(19)-Se(20) bond length is 2.48 Å. In the twentieth Se site, Se(20) is bonded in a distorted trigonal non-coplanar geometry to one Ir(5), one Se(19), and one Se(21) atom. The Se(20)-Se(21) bond length is 2.57 Å. In the twenty-first Se site, Se(21) is bonded in a distorted single-bond geometry to one Ir(6) and one Se(20) atom.