K2CuBr3 crystallizes in the orthorhombic Pnma space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 7-coordinate geometry to two equivalent Br(1), two equivalent Br(3), and three equivalent Br(2) atoms. In the second K site, K(2) is bonded to two equivalent Br(1), two equivalent Br(2), and three equivalent Br(3) atoms to form distorted KBr7 pentagonal bipyramids that share corners with two equivalent K(2)Br7 pentagonal bipyramids,  a cornercorner with one Cu(1)Br4 tetrahedra, edges with four equivalent K(2)Br7 pentagonal bipyramids, and edges with four equivalent Cu(1)Br4 tetrahedra. Cu(1) is bonded to one Br(2), one Br(3), and two equivalent Br(1) atoms to form CuBr4 tetrahedra that share  a cornercorner with one K(2)Br7 pentagonal bipyramid, corners with two equivalent Cu(1)Br4 tetrahedra, and edges with four equivalent K(2)Br7 pentagonal bipyramids. There are three inequivalent Br sites. In the first Br site, Br(1) is bonded to two equivalent K(1), two equivalent K(2), and two equivalent Cu(1) atoms to form distorted BrK4Cu2 octahedra that share corners with two equivalent Br(1)K4Cu2 octahedra, corners with two equivalent Br(2)K5Cu octahedra, corners with five equivalent Br(3)K5Cu octahedra, edges with two equivalent Br(1)K4Cu2 octahedra, edges with two equivalent Br(3)K5Cu octahedra, edges with five equivalent Br(2)K5Cu octahedra, and  a faceface with one Br(3)K5Cu octahedra. The corner-sharing octahedral tilt angles range from 17-61°. In the second Br site, Br(2) is bonded to two equivalent K(2), three equivalent K(1), and one Cu(1) atom to form distorted BrK5Cu octahedra that share corners with two equivalent Br(1)K4Cu2 octahedra, corners with eight equivalent Br(3)K5Cu octahedra,  an edgeedge with one Br(3)K5Cu octahedra, edges with four equivalent Br(2)K5Cu octahedra, edges with five equivalent Br(1)K4Cu2 octahedra, and  a faceface with one Br(3)K5Cu octahedra. The corner-sharing octahedral tilt angles range from 17-56°. In the third Br site, Br(3) is bonded to two equivalent K(1), three equivalent K(2), and one Cu(1) atom to form distorted BrK5Cu octahedra that share corners with five equivalent Br(1)K4Cu2 octahedra, corners with eight equivalent Br(2)K5Cu octahedra,  an edgeedge with one Br(2)K5Cu octahedra, edges with two equivalent Br(1)K4Cu2 octahedra, edges with four equivalent Br(3)K5Cu octahedra,  a faceface with one Br(1)K4Cu2 octahedra, and  a faceface with one Br(2)K5Cu octahedra. The corner-sharing octahedral tilt angles range from 26-61°.
K2CuBr3 crystallizes in the orthorhombic Pnma space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 7-coordinate geometry to two equivalent Br(1), two equivalent Br(3), and three equivalent Br(2) atoms. Both K(1)-Br(1) bond lengths are 3.40 Å. Both K(1)-Br(3) bond lengths are 3.36 Å. There are two shorter (3.31 Å) and one longer (3.40 Å) K(1)-Br(2) bond length. In the second K site, K(2) is bonded to two equivalent Br(1), two equivalent Br(2), and three equivalent Br(3) atoms to form distorted KBr7 pentagonal bipyramids that share corners with two equivalent K(2)Br7 pentagonal bipyramids,  a cornercorner with one Cu(1)Br4 tetrahedra, edges with four equivalent K(2)Br7 pentagonal bipyramids, and edges with four equivalent Cu(1)Br4 tetrahedra. There is one shorter (3.34 Å) and one longer (3.35 Å) K(2)-Br(1) bond length. Both K(2)-Br(2) bond lengths are 3.30 Å. There are two shorter (3.27 Å) and one longer (3.42 Å) K(2)-Br(3) bond length. Cu(1) is bonded to one Br(2), one Br(3), and two equivalent Br(1) atoms to form CuBr4 tetrahedra that share  a cornercorner with one K(2)Br7 pentagonal bipyramid, corners with two equivalent Cu(1)Br4 tetrahedra, and edges with four equivalent K(2)Br7 pentagonal bipyramids. The Cu(1)-Br(2) bond length is 2.46 Å. The Cu(1)-Br(3) bond length is 2.44 Å. Both Cu(1)-Br(1) bond lengths are 2.51 Å. There are three inequivalent Br sites. In the first Br site, Br(1) is bonded to two equivalent K(1), two equivalent K(2), and two equivalent Cu(1) atoms to form distorted BrK4Cu2 octahedra that share corners with two equivalent Br(1)K4Cu2 octahedra, corners with two equivalent Br(2)K5Cu octahedra, corners with five equivalent Br(3)K5Cu octahedra, edges with two equivalent Br(1)K4Cu2 octahedra, edges with two equivalent Br(3)K5Cu octahedra, edges with five equivalent Br(2)K5Cu octahedra, and  a faceface with one Br(3)K5Cu octahedra. The corner-sharing octahedral tilt angles range from 17-61°. In the second Br site, Br(2) is bonded to two equivalent K(2), three equivalent K(1), and one Cu(1) atom to form distorted BrK5Cu octahedra that share corners with two equivalent Br(1)K4Cu2 octahedra, corners with eight equivalent Br(3)K5Cu octahedra,  an edgeedge with one Br(3)K5Cu octahedra, edges with four equivalent Br(2)K5Cu octahedra, edges with five equivalent Br(1)K4Cu2 octahedra, and  a faceface with one Br(3)K5Cu octahedra. The corner-sharing octahedral tilt angles range from 17-56°. In the third Br site, Br(3) is bonded to two equivalent K(1), three equivalent K(2), and one Cu(1) atom to form distorted BrK5Cu octahedra that share corners with five equivalent Br(1)K4Cu2 octahedra, corners with eight equivalent Br(2)K5Cu octahedra,  an edgeedge with one Br(2)K5Cu octahedra, edges with two equivalent Br(1)K4Cu2 octahedra, edges with four equivalent Br(3)K5Cu octahedra,  a faceface with one Br(1)K4Cu2 octahedra, and  a faceface with one Br(2)K5Cu octahedra. The corner-sharing octahedral tilt angles range from 26-61°.