Y2Co7 crystallizes in the trigonal R-3m space group. There are five inequivalent Y sites. In the first Y site, Y(1) is bonded in a 18-coordinate geometry to three equivalent Co(2), three equivalent Co(3), six equivalent Co(4), and six equivalent Co(5) atoms. In the second Y site, Y(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4); and six equivalent Co(5) atoms. In the third Y site, Y(2) is bonded in a 12-coordinate geometry to three equivalent Co(1) and nine equivalent Co(5) atoms. In the fourth Y site, Y(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4); and six equivalent Co(5) atoms. In the fifth Y site, Y(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4); and six equivalent Co(5) atoms. There are seven inequivalent Co sites. In the first Co site, Co(4) is bonded to four Y(1,1); two equivalent Co(2); two equivalent Co(3); and four equivalent Co(4) atoms to form CoY4Co8 cuboctahedra that share corners with four equivalent Co(4)Y4Co8 cuboctahedra, corners with twelve equivalent Co(5)Y5Co7 cuboctahedra, edges with two equivalent Co(4)Y4Co8 cuboctahedra, edges with eight equivalent Co(5)Y5Co7 cuboctahedra, faces with two equivalent Co(5)Y5Co7 cuboctahedra, and faces with eight equivalent Co(4)Y4Co8 cuboctahedra. In the second Co site, Co(1) is bonded to six equivalent Y(2) and six equivalent Co(5) atoms to form CoY6Co6 cuboctahedra that share corners with twelve equivalent Co(5)Y5Co7 cuboctahedra, edges with six equivalent Co(1)Y6Co6 cuboctahedra, and faces with eighteen equivalent Co(5)Y5Co7 cuboctahedra. In the third Co site, Co(2) is bonded in a 9-coordinate geometry to three equivalent Y(1); three Co(4,4); and three equivalent Co(5) atoms. In the fourth Co site, Co(3) is bonded in a 9-coordinate geometry to three equivalent Y(1), three equivalent Co(4), and three equivalent Co(5) atoms. In the fifth Co site, Co(4) is bonded to four equivalent Y(1), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms to form CoY4Co8 cuboctahedra that share corners with four equivalent Co(4)Y4Co8 cuboctahedra, corners with twelve equivalent Co(5)Y5Co7 cuboctahedra, edges with two equivalent Co(4)Y4Co8 cuboctahedra, edges with eight equivalent Co(5)Y5Co7 cuboctahedra, faces with two equivalent Co(5)Y5Co7 cuboctahedra, and faces with eight equivalent Co(4)Y4Co8 cuboctahedra. In the sixth Co site, Co(5) is bonded to two equivalent Y(1), three equivalent Y(2), one Co(1), one Co(2), one Co(3), and four equivalent Co(5) atoms to form distorted CoY5Co7 cuboctahedra that share corners with two equivalent Co(1)Y6Co6 cuboctahedra, corners with six equivalent Co(4)Y4Co8 cuboctahedra, corners with nine equivalent Co(5)Y5Co7 cuboctahedra, edges with four equivalent Co(4)Y4Co8 cuboctahedra, edges with four equivalent Co(5)Y5Co7 cuboctahedra,  a faceface with one Co(4)Y4Co8 cuboctahedra, faces with three equivalent Co(1)Y6Co6 cuboctahedra, and faces with ten equivalent Co(5)Y5Co7 cuboctahedra. In the seventh Co site, Co(4) is bonded to four Y(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoY4Co8 cuboctahedra that share corners with four equivalent Co(4)Y4Co8 cuboctahedra; corners with twelve equivalent Co(5)Y5Co7 cuboctahedra; edges with two equivalent Co(4)Y4Co8 cuboctahedra; edges with eight equivalent Co(5)Y5Co7 cuboctahedra; faces with two equivalent Co(5)Y5Co7 cuboctahedra; and faces with eight Co(4,4)Y4Co8 cuboctahedra.
Y2Co7 crystallizes in the trigonal R-3m space group. There are five inequivalent Y sites. In the first Y site, Y(1) is bonded in a 18-coordinate geometry to three equivalent Co(2), three equivalent Co(3), six equivalent Co(4), and six equivalent Co(5) atoms. All Y(1)-Co(2) bond lengths are 2.87 Å. All Y(1)-Co(3) bond lengths are 2.87 Å. All Y(1)-Co(4) bond lengths are 3.10 Å. All Y(1)-Co(5) bond lengths are 3.25 Å. In the second Y site, Y(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4); and six equivalent Co(5) atoms. All Y(1)-Co(2) bond lengths are 2.87 Å. All Y(1)-Co(3) bond lengths are 2.87 Å. All Y(1)-Co(4,4) bond lengths are 3.10 Å. All Y(1)-Co(5) bond lengths are 3.25 Å. In the third Y site, Y(2) is bonded in a 12-coordinate geometry to three equivalent Co(1) and nine equivalent Co(5) atoms. All Y(2)-Co(1) bond lengths are 2.95 Å. There are six shorter (2.85 Å) and three longer (3.11 Å) Y(2)-Co(5) bond lengths. In the fourth Y site, Y(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4); and six equivalent Co(5) atoms. All Y(1)-Co(2) bond lengths are 2.87 Å. All Y(1)-Co(3) bond lengths are 2.87 Å. All Y(1)-Co(4,4) bond lengths are 3.10 Å. All Y(1)-Co(5) bond lengths are 3.25 Å. In the fifth Y site, Y(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4); and six equivalent Co(5) atoms. All Y(1)-Co(2) bond lengths are 2.87 Å. All Y(1)-Co(3) bond lengths are 2.87 Å. All Y(1)-Co(4,4) bond lengths are 3.10 Å. All Y(1)-Co(5) bond lengths are 3.25 Å. There are seven inequivalent Co sites. In the first Co site, Co(4) is bonded to four Y(1,1); two equivalent Co(2); two equivalent Co(3); and four equivalent Co(4) atoms to form CoY4Co8 cuboctahedra that share corners with four equivalent Co(4)Y4Co8 cuboctahedra, corners with twelve equivalent Co(5)Y5Co7 cuboctahedra, edges with two equivalent Co(4)Y4Co8 cuboctahedra, edges with eight equivalent Co(5)Y5Co7 cuboctahedra, faces with two equivalent Co(5)Y5Co7 cuboctahedra, and faces with eight equivalent Co(4)Y4Co8 cuboctahedra. Both Co(4)-Co(2) bond lengths are 2.43 Å. Both Co(4)-Co(3) bond lengths are 2.45 Å. All Co(4)-Co(4) bond lengths are 2.48 Å. In the second Co site, Co(1) is bonded to six equivalent Y(2) and six equivalent Co(5) atoms to form CoY6Co6 cuboctahedra that share corners with twelve equivalent Co(5)Y5Co7 cuboctahedra, edges with six equivalent Co(1)Y6Co6 cuboctahedra, and faces with eighteen equivalent Co(5)Y5Co7 cuboctahedra. All Co(1)-Co(5) bond lengths are 2.52 Å. In the third Co site, Co(2) is bonded in a 9-coordinate geometry to three equivalent Y(1); three Co(4,4); and three equivalent Co(5) atoms. Both Co(2)-Co(4) bond lengths are 2.43 Å. All Co(2)-Co(5) bond lengths are 2.45 Å. In the fourth Co site, Co(3) is bonded in a 9-coordinate geometry to three equivalent Y(1), three equivalent Co(4), and three equivalent Co(5) atoms. All Co(3)-Co(4) bond lengths are 2.45 Å. All Co(3)-Co(5) bond lengths are 2.42 Å. In the fifth Co site, Co(4) is bonded to four equivalent Y(1), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms to form CoY4Co8 cuboctahedra that share corners with four equivalent Co(4)Y4Co8 cuboctahedra, corners with twelve equivalent Co(5)Y5Co7 cuboctahedra, edges with two equivalent Co(4)Y4Co8 cuboctahedra, edges with eight equivalent Co(5)Y5Co7 cuboctahedra, faces with two equivalent Co(5)Y5Co7 cuboctahedra, and faces with eight equivalent Co(4)Y4Co8 cuboctahedra. Both Co(4)-Co(2) bond lengths are 2.43 Å. All Co(4)-Co(4) bond lengths are 2.48 Å. In the sixth Co site, Co(5) is bonded to two equivalent Y(1), three equivalent Y(2), one Co(1), one Co(2), one Co(3), and four equivalent Co(5) atoms to form distorted CoY5Co7 cuboctahedra that share corners with two equivalent Co(1)Y6Co6 cuboctahedra, corners with six equivalent Co(4)Y4Co8 cuboctahedra, corners with nine equivalent Co(5)Y5Co7 cuboctahedra, edges with four equivalent Co(4)Y4Co8 cuboctahedra, edges with four equivalent Co(5)Y5Co7 cuboctahedra,  a faceface with one Co(4)Y4Co8 cuboctahedra, faces with three equivalent Co(1)Y6Co6 cuboctahedra, and faces with ten equivalent Co(5)Y5Co7 cuboctahedra. There are two shorter (2.48 Å) and two longer (2.49 Å) Co(5)-Co(5) bond lengths. In the seventh Co site, Co(4) is bonded to four Y(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoY4Co8 cuboctahedra that share corners with four equivalent Co(4)Y4Co8 cuboctahedra; corners with twelve equivalent Co(5)Y5Co7 cuboctahedra; edges with two equivalent Co(4)Y4Co8 cuboctahedra; edges with eight equivalent Co(5)Y5Co7 cuboctahedra; faces with two equivalent Co(5)Y5Co7 cuboctahedra; and faces with eight Co(4,4)Y4Co8 cuboctahedra. Both Co(4)-Co(3) bond lengths are 2.45 Å. Both Co(4)-Co(4) bond lengths are 2.48 Å.