Er3RuI3 crystallizes in the monoclinic P2_1/m space group. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to two equivalent Ru(1), one I(3), and three equivalent I(1) atoms. In the second Er site, Er(2) is bonded to three equivalent Ru(1), one I(2), and two equivalent I(1) atoms to form distorted edge-sharing ErRu3I3 octahedra. In the third Er site, Er(3) is bonded in a 6-coordinate geometry to one Ru(1), two equivalent I(3), and three equivalent I(2) atoms. Ru(1) is bonded in a 6-coordinate geometry to one Er(3), two equivalent Er(1), and three equivalent Er(2) atoms. There are three inequivalent I sites. In the first I site, I(1) is bonded in a 5-coordinate geometry to two equivalent Er(2) and three equivalent Er(1) atoms. In the second I site, I(2) is bonded in a 4-coordinate geometry to one Er(2) and three equivalent Er(3) atoms. In the third I site, I(3) is bonded in a distorted T-shaped geometry to one Er(1) and two equivalent Er(3) atoms.
Er3RuI3 crystallizes in the monoclinic P2_1/m space group. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to two equivalent Ru(1), one I(3), and three equivalent I(1) atoms. Both Er(1)-Ru(1) bond lengths are 2.75 Å. The Er(1)-I(3) bond length is 3.25 Å. There is one shorter (3.34 Å) and two longer (3.48 Å) Er(1)-I(1) bond lengths. In the second Er site, Er(2) is bonded to three equivalent Ru(1), one I(2), and two equivalent I(1) atoms to form distorted edge-sharing ErRu3I3 octahedra. There are two shorter (2.69 Å) and one longer (2.78 Å) Er(2)-Ru(1) bond length. The Er(2)-I(2) bond length is 3.23 Å. Both Er(2)-I(1) bond lengths are 3.31 Å. In the third Er site, Er(3) is bonded in a 6-coordinate geometry to one Ru(1), two equivalent I(3), and three equivalent I(2) atoms. The Er(3)-Ru(1) bond length is 2.70 Å. Both Er(3)-I(3) bond lengths are 3.09 Å. There are two shorter (3.17 Å) and one longer (3.57 Å) Er(3)-I(2) bond length. Ru(1) is bonded in a 6-coordinate geometry to one Er(3), two equivalent Er(1), and three equivalent Er(2) atoms. There are three inequivalent I sites. In the first I site, I(1) is bonded in a 5-coordinate geometry to two equivalent Er(2) and three equivalent Er(1) atoms. In the second I site, I(2) is bonded in a 4-coordinate geometry to one Er(2) and three equivalent Er(3) atoms. In the third I site, I(3) is bonded in a distorted T-shaped geometry to one Er(1) and two equivalent Er(3) atoms.