KMg14C crystallizes in the orthorhombic Amm2 space group. K(1) is bonded to two equivalent Mg(6), four equivalent Mg(3), four equivalent Mg(5), and two equivalent C(1) atoms to form KMg10C2 cuboctahedra that share corners with four equivalent Mg(2)Mg12 cuboctahedra, corners with six equivalent K(1)Mg10C2 cuboctahedra, corners with eight equivalent Mg(4)Mg12 cuboctahedra, and faces with two equivalent Mg(1)Mg12 cuboctahedra. There are seven inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2), two equivalent Mg(6), four equivalent Mg(4), and four equivalent Mg(5) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(1)Mg12 cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent K(1)Mg10C2 cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, and faces with four equivalent Mg(4)Mg12 cuboctahedra. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1), two equivalent Mg(7), four equivalent Mg(4), and four equivalent Mg(5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent K(1)Mg10C2 cuboctahedra, corners with six equivalent Mg(2)Mg12 cuboctahedra, edges with two equivalent Mg(1)Mg12 cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, and faces with four equivalent Mg(4)Mg12 cuboctahedra. In the third Mg site, Mg(3) is bonded in a single-bond geometry to two equivalent K(1), two equivalent Mg(6), two equivalent Mg(7), and one C(1) atom. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), two equivalent Mg(6), and two equivalent Mg(7) atoms to form distorted MgMg12 cuboctahedra that share corners with four equivalent K(1)Mg10C2 cuboctahedra, corners with six equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Mg(1)Mg12 cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, and faces with two equivalent Mg(4)Mg12 cuboctahedra. In the fifth Mg site, Mg(5) is bonded in a 12-coordinate geometry to one K(1), one Mg(1), one Mg(2), one Mg(4), two equivalent Mg(6), and two equivalent Mg(7) atoms. In the sixth Mg site, Mg(6) is bonded in a 12-coordinate geometry to one K(1), one Mg(1), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(7), and four equivalent Mg(5) atoms. In the seventh Mg site, Mg(7) is bonded in a 11-coordinate geometry to one Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(6), and four equivalent Mg(5) atoms. C(1) is bonded in an L-shaped geometry to two equivalent K(1) and two equivalent Mg(3) atoms.
KMg14C crystallizes in the orthorhombic Amm2 space group. K(1) is bonded to two equivalent Mg(6), four equivalent Mg(3), four equivalent Mg(5), and two equivalent C(1) atoms to form KMg10C2 cuboctahedra that share corners with four equivalent Mg(2)Mg12 cuboctahedra, corners with six equivalent K(1)Mg10C2 cuboctahedra, corners with eight equivalent Mg(4)Mg12 cuboctahedra, and faces with two equivalent Mg(1)Mg12 cuboctahedra. Both K(1)-Mg(6) bond lengths are 3.23 Å. There are two shorter (3.28 Å) and two longer (3.33 Å) K(1)-Mg(3) bond lengths. All K(1)-Mg(5) bond lengths are 3.31 Å. Both K(1)-C(1) bond lengths are 3.37 Å. There are seven inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2), two equivalent Mg(6), four equivalent Mg(4), and four equivalent Mg(5) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(1)Mg12 cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent K(1)Mg10C2 cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, and faces with four equivalent Mg(4)Mg12 cuboctahedra. Both Mg(1)-Mg(2) bond lengths are 3.12 Å. Both Mg(1)-Mg(6) bond lengths are 3.12 Å. There are two shorter (3.20 Å) and two longer (3.41 Å) Mg(1)-Mg(4) bond lengths. All Mg(1)-Mg(5) bond lengths are 3.19 Å. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1), two equivalent Mg(7), four equivalent Mg(4), and four equivalent Mg(5) atoms to form MgMg12 cuboctahedra that share corners with four equivalent K(1)Mg10C2 cuboctahedra, corners with six equivalent Mg(2)Mg12 cuboctahedra, edges with two equivalent Mg(1)Mg12 cuboctahedra, edges with four equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, and faces with four equivalent Mg(4)Mg12 cuboctahedra. Both Mg(2)-Mg(7) bond lengths are 3.37 Å. There are two shorter (3.29 Å) and two longer (3.33 Å) Mg(2)-Mg(4) bond lengths. All Mg(2)-Mg(5) bond lengths are 3.16 Å. In the third Mg site, Mg(3) is bonded in a single-bond geometry to two equivalent K(1), two equivalent Mg(6), two equivalent Mg(7), and one C(1) atom. Both Mg(3)-Mg(6) bond lengths are 3.40 Å. Both Mg(3)-Mg(7) bond lengths are 3.13 Å. The Mg(3)-C(1) bond length is 2.18 Å. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), two equivalent Mg(6), and two equivalent Mg(7) atoms to form distorted MgMg12 cuboctahedra that share corners with four equivalent K(1)Mg10C2 cuboctahedra, corners with six equivalent Mg(4)Mg12 cuboctahedra, edges with two equivalent Mg(1)Mg12 cuboctahedra, edges with two equivalent Mg(2)Mg12 cuboctahedra, edges with two equivalent Mg(4)Mg12 cuboctahedra, faces with two equivalent Mg(1)Mg12 cuboctahedra, faces with two equivalent Mg(2)Mg12 cuboctahedra, and faces with two equivalent Mg(4)Mg12 cuboctahedra. There is one shorter (3.05 Å) and one longer (3.18 Å) Mg(4)-Mg(4) bond length. Both Mg(4)-Mg(5) bond lengths are 3.17 Å. Both Mg(4)-Mg(6) bond lengths are 3.03 Å. Both Mg(4)-Mg(7) bond lengths are 3.44 Å. In the fifth Mg site, Mg(5) is bonded in a 12-coordinate geometry to one K(1), one Mg(1), one Mg(2), one Mg(4), two equivalent Mg(6), and two equivalent Mg(7) atoms. There is one shorter (3.22 Å) and one longer (3.40 Å) Mg(5)-Mg(6) bond length. There is one shorter (3.23 Å) and one longer (3.41 Å) Mg(5)-Mg(7) bond length. In the sixth Mg site, Mg(6) is bonded in a 12-coordinate geometry to one K(1), one Mg(1), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(7), and four equivalent Mg(5) atoms. Both Mg(6)-Mg(7) bond lengths are 3.16 Å. In the seventh Mg site, Mg(7) is bonded in a 11-coordinate geometry to one Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(6), and four equivalent Mg(5) atoms. C(1) is bonded in an L-shaped geometry to two equivalent K(1) and two equivalent Mg(3) atoms.