GdMoC2 crystallizes in the orthorhombic Pnma space group. Gd(1) is bonded to three equivalent C(2) and four equivalent C(1) atoms to form distorted GdC7 pentagonal bipyramids that share corners with four equivalent Gd(1)C7 pentagonal bipyramids, corners with three equivalent Mo(1)C5 trigonal bipyramids, edges with four equivalent Gd(1)C7 pentagonal bipyramids, edges with seven equivalent Mo(1)C5 trigonal bipyramids, and faces with two equivalent Gd(1)C7 pentagonal bipyramids. Mo(1) is bonded to two equivalent C(1) and three equivalent C(2) atoms to form MoC5 trigonal bipyramids that share corners with three equivalent Gd(1)C7 pentagonal bipyramids, corners with four equivalent Mo(1)C5 trigonal bipyramids, edges with seven equivalent Gd(1)C7 pentagonal bipyramids, and edges with two equivalent Mo(1)C5 trigonal bipyramids. There are two inequivalent C sites. In the first C site, C(1) is bonded to four equivalent Gd(1) and two equivalent Mo(1) atoms to form CGd4Mo2 octahedra that share corners with four equivalent C(1)Gd4Mo2 octahedra, corners with nine equivalent C(2)Gd3Mo3 octahedra, edges with two equivalent C(1)Gd4Mo2 octahedra, edges with three equivalent C(2)Gd3Mo3 octahedra,  a faceface with one C(2)Gd3Mo3 octahedra, and faces with two equivalent C(1)Gd4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 9-60°. In the second C site, C(2) is bonded to three equivalent Gd(1) and three equivalent Mo(1) atoms to form CGd3Mo3 octahedra that share corners with nine equivalent C(1)Gd4Mo2 octahedra, edges with three equivalent C(1)Gd4Mo2 octahedra, edges with six equivalent C(2)Gd3Mo3 octahedra, and  a faceface with one C(1)Gd4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 9-60°.
GdMoC2 crystallizes in the orthorhombic Pnma space group. Gd(1) is bonded to three equivalent C(2) and four equivalent C(1) atoms to form distorted GdC7 pentagonal bipyramids that share corners with four equivalent Gd(1)C7 pentagonal bipyramids, corners with three equivalent Mo(1)C5 trigonal bipyramids, edges with four equivalent Gd(1)C7 pentagonal bipyramids, edges with seven equivalent Mo(1)C5 trigonal bipyramids, and faces with two equivalent Gd(1)C7 pentagonal bipyramids. There is one shorter (2.47 Å) and two longer (2.67 Å) Gd(1)-C(2) bond lengths. There are two shorter (2.51 Å) and two longer (2.58 Å) Gd(1)-C(1) bond lengths. Mo(1) is bonded to two equivalent C(1) and three equivalent C(2) atoms to form MoC5 trigonal bipyramids that share corners with three equivalent Gd(1)C7 pentagonal bipyramids, corners with four equivalent Mo(1)C5 trigonal bipyramids, edges with seven equivalent Gd(1)C7 pentagonal bipyramids, and edges with two equivalent Mo(1)C5 trigonal bipyramids. There is one shorter (2.07 Å) and one longer (2.12 Å) Mo(1)-C(1) bond length. There are two shorter (2.10 Å) and one longer (2.26 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 Gd(1) and two equivalent Mo(1) atoms to form CGd4Mo2 octahedra that share corners with four equivalent C(1)Gd4Mo2 octahedra, corners with nine equivalent C(2)Gd3Mo3 octahedra, edges with two equivalent C(1)Gd4Mo2 octahedra, edges with three equivalent C(2)Gd3Mo3 octahedra,  a faceface with one C(2)Gd3Mo3 octahedra, and faces with two equivalent C(1)Gd4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 9-60°. In the second C site, C(2) is bonded to three equivalent Gd(1) and three equivalent Mo(1) atoms to form CGd3Mo3 octahedra that share corners with nine equivalent C(1)Gd4Mo2 octahedra, edges with three equivalent C(1)Gd4Mo2 octahedra, edges with six equivalent C(2)Gd3Mo3 octahedra, and  a faceface with one C(1)Gd4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 9-60°.