Pd2TlSe3 is Ilmenite-like structured and crystallizes in the trigonal P-3m1 space group. There are two inequivalent Pd sites. In the first Pd site, Pd(1) is bonded to six equivalent Se(1) atoms to form edge-sharing PdSe6 octahedra. In the second Pd site, Pd(2) is bonded to two equivalent Tl(1) and four equivalent Se(1) atoms to form PdTl2Se4 octahedra that share corners with six equivalent Se(1)TlPd3 trigonal pyramids, edges with two equivalent Pd(1)Se6 octahedra, and edges with four equivalent Pd(2)Tl2Se4 octahedra. Tl(1) is bonded in a 6-coordinate geometry to three equivalent Pd(2) and three equivalent Se(1) atoms. Se(1) is bonded to one Pd(1), two equivalent Pd(2), and one Tl(1) atom to form distorted SeTlPd3 trigonal pyramids that share corners with three equivalent Pd(2)Tl2Se4 octahedra, corners with five equivalent Se(1)TlPd3 trigonal pyramids, and edges with four equivalent Se(1)TlPd3 trigonal pyramids. The corner-sharing octahedral tilt angles range from 6-72°.
Pd2TlSe3 is Ilmenite-like structured and crystallizes in the trigonal P-3m1 space group. There are two inequivalent Pd sites. In the first Pd site, Pd(1) is bonded to six equivalent Se(1) atoms to form edge-sharing PdSe6 octahedra. All Pd(1)-Se(1) bond lengths are 2.52 Å. In the second Pd site, Pd(2) is bonded to two equivalent Tl(1) and four equivalent Se(1) atoms to form PdTl2Se4 octahedra that share corners with six equivalent Se(1)TlPd3 trigonal pyramids, edges with two equivalent Pd(1)Se6 octahedra, and edges with four equivalent Pd(2)Tl2Se4 octahedra. Both Pd(2)-Tl(1) bond lengths are 3.02 Å. All Pd(2)-Se(1) bond lengths are 2.48 Å. Tl(1) is bonded in a 6-coordinate geometry to three equivalent Pd(2) and three equivalent Se(1) atoms. All Tl(1)-Se(1) bond lengths are 3.31 Å. Se(1) is bonded to one Pd(1), two equivalent Pd(2), and one Tl(1) atom to form distorted SeTlPd3 trigonal pyramids that share corners with three equivalent Pd(2)Tl2Se4 octahedra, corners with five equivalent Se(1)TlPd3 trigonal pyramids, and edges with four equivalent Se(1)TlPd3 trigonal pyramids. The corner-sharing octahedral tilt angles range from 6-72°.