Al6C3N2 crystallizes in the monoclinic Pm space group. There are six inequivalent Al sites. In the first Al site, Al(1) is bonded in a 5-coordinate geometry to one C(2), two equivalent C(3), and two equivalent N(2) atoms. In the second Al site, Al(2) is bonded in a distorted bent 150 degrees geometry to one C(1) and one C(2) atom. In the third Al site, Al(3) is bonded in a bent 120 degrees geometry to two equivalent C(2) atoms. In the fourth Al site, Al(4) is bonded in a distorted see-saw-like geometry to two equivalent C(1) and two equivalent N(1) atoms. In the fifth Al site, Al(5) is bonded to two equivalent C(3), one N(1), and two equivalent N(2) atoms to form AlC2N3 trigonal bipyramids that share corners with two equivalent C(2)Al4N trigonal bipyramids, corners with four equivalent Al(5)C2N3 trigonal bipyramids, and edges with two equivalent Al(6)C3N2 trigonal bipyramids. In the sixth Al site, Al(6) is bonded to one C(3), two equivalent C(1), and two equivalent N(1) atoms to form AlC3N2 trigonal bipyramids that share corners with four equivalent Al(6)C3N2 trigonal bipyramids and edges with two equivalent Al(5)C2N3 trigonal bipyramids. There are three inequivalent C sites. In the first C site, C(1) is bonded to one Al(2), two equivalent Al(4), and two equivalent Al(6) atoms to form CAl5 trigonal bipyramids that share  a cornercorner with one C(2)Al4N trigonal bipyramid, corners with two equivalent C(3)Al5 trigonal bipyramids, corners with four equivalent C(1)Al5 trigonal bipyramids, and edges with four equivalent N(1)Al5 trigonal bipyramids. In the second C site, C(2) is bonded to one Al(1), one Al(2), two equivalent Al(3), and one N(2) atom to form distorted CAl4N trigonal bipyramids that share  a cornercorner with one C(1)Al5 trigonal bipyramid, corners with two equivalent Al(5)C2N3 trigonal bipyramids, corners with two equivalent C(2)Al4N trigonal bipyramids, and corners with two equivalent C(3)Al5 trigonal bipyramids. In the third C site, C(3) is bonded to one Al(6), two equivalent Al(1), and two equivalent Al(5) atoms to form CAl5 trigonal bipyramids that share corners with two equivalent C(2)Al4N trigonal bipyramids, corners with two equivalent C(1)Al5 trigonal bipyramids, corners with four equivalent C(3)Al5 trigonal bipyramids, and edges with two equivalent N(1)Al5 trigonal bipyramids. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Al(5), two equivalent Al(4), and two equivalent Al(6) atoms to form NAl5 trigonal bipyramids that share corners with four equivalent N(1)Al5 trigonal bipyramids, edges with two equivalent C(3)Al5 trigonal bipyramids, and edges with four equivalent C(1)Al5 trigonal bipyramids. In the second N site, N(2) is bonded in a 5-coordinate geometry to two equivalent Al(1), two equivalent Al(5), and one C(2) atom.
Al6C3N2 crystallizes in the monoclinic Pm space group. There are six inequivalent Al sites. In the first Al site, Al(1) is bonded in a 5-coordinate geometry to one C(2), two equivalent C(3), and two equivalent N(2) atoms. The Al(1)-C(2) bond length is 2.12 Å. Both Al(1)-C(3) bond lengths are 1.92 Å. There is one shorter (1.96 Å) and one longer (2.25 Å) Al(1)-N(2) bond length. In the second Al site, Al(2) is bonded in a distorted bent 150 degrees geometry to one C(1) and one C(2) atom. The Al(2)-C(1) bond length is 1.92 Å. The Al(2)-C(2) bond length is 2.06 Å. In the third Al site, Al(3) is bonded in a bent 120 degrees geometry to two equivalent C(2) atoms. Both Al(3)-C(2) bond lengths are 2.06 Å. In the fourth Al site, Al(4) is bonded in a distorted see-saw-like geometry to two equivalent C(1) and two equivalent N(1) atoms. There is one shorter (2.09 Å) and one longer (2.14 Å) Al(4)-C(1) bond length. Both Al(4)-N(1) bond lengths are 1.92 Å. In the fifth Al site, Al(5) is bonded to two equivalent C(3), one N(1), and two equivalent N(2) atoms to form AlC2N3 trigonal bipyramids that share corners with two equivalent C(2)Al4N trigonal bipyramids, corners with four equivalent Al(5)C2N3 trigonal bipyramids, and edges with two equivalent Al(6)C3N2 trigonal bipyramids. There is one shorter (2.06 Å) and one longer (2.10 Å) Al(5)-C(3) bond length. The Al(5)-N(1) bond length is 1.96 Å. Both Al(5)-N(2) bond lengths are 2.04 Å. In the sixth Al site, Al(6) is bonded to one C(3), two equivalent C(1), and two equivalent N(1) atoms to form AlC3N2 trigonal bipyramids that share corners with four equivalent Al(6)C3N2 trigonal bipyramids and edges with two equivalent Al(5)C2N3 trigonal bipyramids. The Al(6)-C(3) bond length is 2.04 Å. Both Al(6)-C(1) bond lengths are 2.04 Å. There is one shorter (2.08 Å) and one longer (2.09 Å) Al(6)-N(1) bond length. There are three inequivalent C sites. In the first C site, C(1) is bonded to one Al(2), two equivalent Al(4), and two equivalent Al(6) atoms to form CAl5 trigonal bipyramids that share  a cornercorner with one C(2)Al4N trigonal bipyramid, corners with two equivalent C(3)Al5 trigonal bipyramids, corners with four equivalent C(1)Al5 trigonal bipyramids, and edges with four equivalent N(1)Al5 trigonal bipyramids. In the second C site, C(2) is bonded to one Al(1), one Al(2), two equivalent Al(3), and one N(2) atom to form distorted CAl4N trigonal bipyramids that share  a cornercorner with one C(1)Al5 trigonal bipyramid, corners with two equivalent Al(5)C2N3 trigonal bipyramids, corners with two equivalent C(2)Al4N trigonal bipyramids, and corners with two equivalent C(3)Al5 trigonal bipyramids. The C(2)-N(2) bond length is 1.47 Å. In the third C site, C(3) is bonded to one Al(6), two equivalent Al(1), and two equivalent Al(5) atoms to form CAl5 trigonal bipyramids that share corners with two equivalent C(2)Al4N trigonal bipyramids, corners with two equivalent C(1)Al5 trigonal bipyramids, corners with four equivalent C(3)Al5 trigonal bipyramids, and edges with two equivalent N(1)Al5 trigonal bipyramids. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Al(5), two equivalent Al(4), and two equivalent Al(6) atoms to form NAl5 trigonal bipyramids that share corners with four equivalent N(1)Al5 trigonal bipyramids, edges with two equivalent C(3)Al5 trigonal bipyramids, and edges with four equivalent C(1)Al5 trigonal bipyramids. In the second N site, N(2) is bonded in a 5-coordinate geometry to two equivalent Al(1), two equivalent Al(5), and one C(2) atom.