U2Mo2C3 crystallizes in the monoclinic C2/m space group. U(1) is bonded in a distorted pentagonal planar geometry to two equivalent C(1) and three equivalent C(2) atoms. Mo(1) is bonded to one C(1) and three equivalent C(2) atoms to form a mixture of distorted corner and edge-sharing MoC4 trigonal pyramids. There are two inequivalent C sites. In the first C site, C(1) is bonded to four equivalent U(1) and two equivalent Mo(1) atoms to form CU4Mo2 octahedra that share corners with twelve equivalent C(2)U3Mo3 octahedra, edges with two equivalent C(1)U4Mo2 octahedra, and faces with two equivalent C(2)U3Mo3 octahedra. The corner-sharing octahedral tilt angles range from 40-59°. In the second C site, C(2) is bonded to three equivalent U(1) and three equivalent Mo(1) atoms to form CU3Mo3 octahedra that share corners with six equivalent C(1)U4Mo2 octahedra, edges with six equivalent C(2)U3Mo3 octahedra, and  a faceface with one C(1)U4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 40-59°.
U2Mo2C3 crystallizes in the monoclinic C2/m space group. U(1) is bonded in a distorted pentagonal planar geometry to two equivalent C(1) and three equivalent C(2) atoms. Both U(1)-C(1) bond lengths are 2.46 Å. All U(1)-C(2) bond lengths are 2.43 Å. Mo(1) is bonded to one C(1) and three equivalent C(2) atoms to form a mixture of distorted corner and edge-sharing MoC4 trigonal pyramids. The Mo(1)-C(1) bond length is 2.11 Å. There are two shorter (2.13 Å) and one longer (2.18 Å) Mo(1)-C(2) bond length. There are two inequivalent C sites. In the first C site, C(1) is bonded to four equivalent U(1) and two equivalent Mo(1) atoms to form CU4Mo2 octahedra that share corners with twelve equivalent C(2)U3Mo3 octahedra, edges with two equivalent C(1)U4Mo2 octahedra, and faces with two equivalent C(2)U3Mo3 octahedra. The corner-sharing octahedral tilt angles range from 40-59°. In the second C site, C(2) is bonded to three equivalent U(1) and three equivalent Mo(1) atoms to form CU3Mo3 octahedra that share corners with six equivalent C(1)U4Mo2 octahedra, edges with six equivalent C(2)U3Mo3 octahedra, and  a faceface with one C(1)U4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 40-59°.