Er2Mo2C3 crystallizes in the monoclinic C2/m space group. Er(1) is bonded to two equivalent C(2) and three equivalent C(1) atoms to form a mixture of edge and corner-sharing ErC5 square pyramids. Mo(1) is bonded in a distorted see-saw-like geometry to one C(2) and three equivalent C(1) atoms. There are two inequivalent C sites. In the first C site, C(1) is bonded to three equivalent Er(1) and three equivalent Mo(1) atoms to form CEr3Mo3 octahedra that share corners with three equivalent C(2)Er4Mo2 octahedra, edges with three equivalent C(2)Er4Mo2 octahedra, and edges with six equivalent C(1)Er3Mo3 octahedra. The corner-sharing octahedral tilt angles range from 10-28°. In the second C site, C(2) is bonded to four equivalent Er(1) and two equivalent Mo(1) atoms to form CEr4Mo2 octahedra that share corners with six equivalent C(1)Er3Mo3 octahedra, edges with two equivalent C(2)Er4Mo2 octahedra, and edges with six equivalent C(1)Er3Mo3 octahedra. The corner-sharing octahedral tilt angles range from 10-28°.
Er2Mo2C3 crystallizes in the monoclinic C2/m space group. Er(1) is bonded to two equivalent C(2) and three equivalent C(1) atoms to form a mixture of edge and corner-sharing ErC5 square pyramids. Both Er(1)-C(2) bond lengths are 2.51 Å. There is one shorter (2.41 Å) and two longer (2.48 Å) Er(1)-C(1) bond lengths. Mo(1) is bonded in a distorted see-saw-like geometry to one C(2) and three equivalent C(1) atoms. The Mo(1)-C(2) bond length is 2.05 Å. There are two shorter (2.09 Å) and one longer (2.16 Å) Mo(1)-C(1) bond length. There are two inequivalent C sites. In the first C site, C(1) is bonded to three equivalent Er(1) and three equivalent Mo(1) atoms to form CEr3Mo3 octahedra that share corners with three equivalent C(2)Er4Mo2 octahedra, edges with three equivalent C(2)Er4Mo2 octahedra, and edges with six equivalent C(1)Er3Mo3 octahedra. The corner-sharing octahedral tilt angles range from 10-28°. In the second C site, C(2) is bonded to four equivalent Er(1) and two equivalent Mo(1) atoms to form CEr4Mo2 octahedra that share corners with six equivalent C(1)Er3Mo3 octahedra, edges with two equivalent C(2)Er4Mo2 octahedra, and edges with six equivalent C(1)Er3Mo3 octahedra. The corner-sharing octahedral tilt angles range from 10-28°.