BC5 crystallizes in the triclinic P-1 space group. B(1) is bonded to one C(1), one C(2), one C(3), and one C(4) atom to form BC4 tetrahedra that share corners with two equivalent C(1)BC3 tetrahedra, corners with two equivalent C(2)BC3 tetrahedra, corners with two equivalent C(4)BC3 tetrahedra, corners with three equivalent C(3)BC3 tetrahedra, and corners with three equivalent C(5)C4 tetrahedra. There are five inequivalent C sites. In the first C site, C(1) is bonded to one B(1), one C(2), one C(3), and one C(5) atom to form distorted CBC3 tetrahedra that share corners with two equivalent B(1)C4 tetrahedra, corners with two equivalent C(3)BC3 tetrahedra, corners with two equivalent C(5)C4 tetrahedra, corners with three equivalent C(2)BC3 tetrahedra, and corners with three equivalent C(4)BC3 tetrahedra. In the second C site, C(2) is bonded to one B(1), one C(1), one C(3), and one C(5) atom to form distorted CBC3 tetrahedra that share corners with two equivalent B(1)C4 tetrahedra, corners with two equivalent C(3)BC3 tetrahedra, corners with two equivalent C(5)C4 tetrahedra, corners with three equivalent C(1)BC3 tetrahedra, and corners with three equivalent C(4)BC3 tetrahedra. In the third C site, C(3) is bonded to one B(1), one C(1), one C(2), and one C(4) atom to form CBC3 tetrahedra that share corners with two equivalent C(1)BC3 tetrahedra, corners with two equivalent C(2)BC3 tetrahedra, corners with two equivalent C(4)BC3 tetrahedra, corners with three equivalent B(1)C4 tetrahedra, and corners with three equivalent C(5)C4 tetrahedra. In the fourth C site, C(4) is bonded to one B(1), one C(3), one C(4), and one C(5) atom to form distorted CBC3 tetrahedra that share corners with two equivalent B(1)C4 tetrahedra, corners with two equivalent C(3)BC3 tetrahedra, corners with two equivalent C(5)C4 tetrahedra, corners with three equivalent C(1)BC3 tetrahedra, and corners with three equivalent C(2)BC3 tetrahedra. In the fifth C site, C(5) is bonded to one C(1), one C(2), one C(4), and one C(5) atom to form CC4 tetrahedra that share corners with two equivalent C(1)BC3 tetrahedra, corners with two equivalent C(2)BC3 tetrahedra, corners with two equivalent C(4)BC3 tetrahedra, corners with three equivalent B(1)C4 tetrahedra, and corners with three equivalent C(3)BC3 tetrahedra.
BC5 crystallizes in the triclinic P-1 space group. B(1) is bonded to one C(1), one C(2), one C(3), and one C(4) atom to form BC4 tetrahedra that share corners with two equivalent C(1)BC3 tetrahedra, corners with two equivalent C(2)BC3 tetrahedra, corners with two equivalent C(4)BC3 tetrahedra, corners with three equivalent C(3)BC3 tetrahedra, and corners with three equivalent C(5)C4 tetrahedra. The B(1)-C(1) bond length is 1.62 Å. The B(1)-C(2) bond length is 1.61 Å. The B(1)-C(3) bond length is 1.65 Å. The B(1)-C(4) bond length is 1.65 Å. There are five inequivalent C sites. In the first C site, C(1) is bonded to one B(1), one C(2), one C(3), and one C(5) atom to form distorted CBC3 tetrahedra that share corners with two equivalent B(1)C4 tetrahedra, corners with two equivalent C(3)BC3 tetrahedra, corners with two equivalent C(5)C4 tetrahedra, corners with three equivalent C(2)BC3 tetrahedra, and corners with three equivalent C(4)BC3 tetrahedra. The C(1)-C(2) bond length is 1.55 Å. The C(1)-C(3) bond length is 1.54 Å. The C(1)-C(5) bond length is 1.56 Å. In the second C site, C(2) is bonded to one B(1), one C(1), one C(3), and one C(5) atom to form distorted CBC3 tetrahedra that share corners with two equivalent B(1)C4 tetrahedra, corners with two equivalent C(3)BC3 tetrahedra, corners with two equivalent C(5)C4 tetrahedra, corners with three equivalent C(1)BC3 tetrahedra, and corners with three equivalent C(4)BC3 tetrahedra. The C(2)-C(3) bond length is 1.55 Å. The C(2)-C(5) bond length is 1.56 Å. In the third C site, C(3) is bonded to one B(1), one C(1), one C(2), and one C(4) atom to form CBC3 tetrahedra that share corners with two equivalent C(1)BC3 tetrahedra, corners with two equivalent C(2)BC3 tetrahedra, corners with two equivalent C(4)BC3 tetrahedra, corners with three equivalent B(1)C4 tetrahedra, and corners with three equivalent C(5)C4 tetrahedra. The C(3)-C(4) bond length is 1.52 Å. In the fourth C site, C(4) is bonded to one B(1), one C(3), one C(4), and one C(5) atom to form distorted CBC3 tetrahedra that share corners with two equivalent B(1)C4 tetrahedra, corners with two equivalent C(3)BC3 tetrahedra, corners with two equivalent C(5)C4 tetrahedra, corners with three equivalent C(1)BC3 tetrahedra, and corners with three equivalent C(2)BC3 tetrahedra. The C(4)-C(4) bond length is 1.55 Å. The C(4)-C(5) bond length is 1.55 Å. In the fifth C site, C(5) is bonded to one C(1), one C(2), one C(4), and one C(5) atom to form CC4 tetrahedra that share corners with two equivalent C(1)BC3 tetrahedra, corners with two equivalent C(2)BC3 tetrahedra, corners with two equivalent C(4)BC3 tetrahedra, corners with three equivalent B(1)C4 tetrahedra, and corners with three equivalent C(3)BC3 tetrahedra. The C(5)-C(5) bond length is 1.58 Å.