B8O crystallizes in the monoclinic C2/m space group. There are fourteen inequivalent B sites. In the first B site, B(1) is bonded in a single-bond geometry to one B(2), two equivalent B(5), and one O(1) atom. In the second B site, B(2) is bonded in a 6-coordinate geometry to one B(1), one B(2), two equivalent B(5), and two equivalent B(9) atoms. In the third B site, B(3) is bonded in a 6-coordinate geometry to one B(10), one B(3), one B(4), one B(6), one B(7), and one B(8) atom. In the fourth B site, B(4) is bonded in a 6-coordinate geometry to one B(10), one B(3), one B(5), one B(6), one B(7), and one B(8) atom. In the fifth B site, B(5) is bonded in a 6-coordinate geometry to one B(1), one B(2), one B(4), one B(5), and two equivalent B(9) atoms. In the sixth B site, B(6) is bonded in a single-bond geometry to one B(10), one B(3), one B(4), one B(7), and one O(1) atom. In the seventh B site, B(7) is bonded in a 6-coordinate geometry to one B(10), one B(11), one B(3), one B(4), one B(6), and one B(8) atom. In the eighth B site, B(8) is bonded in a single-bond geometry to one B(10), one B(3), one B(4), one B(7), and one O(2) atom. In the ninth B site, B(9) is bonded in a single-bond geometry to one B(2), two equivalent B(5), and one O(2) atom. In the tenth B site, B(10) is bonded in a 7-coordinate geometry to one B(10), one B(14), one B(3), one B(4), one B(6), one B(7), and one B(8) atom. In the eleventh B site, B(11) is bonded in a 6-coordinate geometry to one B(11), one B(13), one B(14), one B(7), and two equivalent B(12) atoms. In the twelfth B site, B(12) is bonded in a single-bond geometry to one B(13), one B(14), two equivalent B(11), and one O(2) atom. In the thirteenth B site, B(13) is bonded in a 6-coordinate geometry to one B(13), one B(14), two equivalent B(11), and two equivalent B(12) atoms. In the fourteenth B site, B(14) is bonded in a 7-coordinate geometry to one B(13), two equivalent B(10), two equivalent B(11), and two equivalent B(12) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one B(1) and two equivalent B(6) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one B(12), one B(8), and one B(9) atom.
B8O crystallizes in the monoclinic C2/m space group. There are fourteen inequivalent B sites. In the first B site, B(1) is bonded in a single-bond geometry to one B(2), two equivalent B(5), and one O(1) atom. The B(1)-B(2) bond length is 1.81 Å. Both B(1)-B(5) bond lengths are 1.77 Å. The B(1)-O(1) bond length is 1.48 Å. In the second B site, B(2) is bonded in a 6-coordinate geometry to one B(1), one B(2), two equivalent B(5), and two equivalent B(9) atoms. The B(2)-B(2) bond length is 1.69 Å. Both B(2)-B(5) bond lengths are 1.77 Å. Both B(2)-B(9) bond lengths are 1.77 Å. In the third B site, B(3) is bonded in a 6-coordinate geometry to one B(10), one B(3), one B(4), one B(6), one B(7), and one B(8) atom. The B(3)-B(10) bond length is 1.83 Å. The B(3)-B(3) bond length is 1.69 Å. The B(3)-B(4) bond length is 1.76 Å. The B(3)-B(6) bond length is 1.80 Å. The B(3)-B(7) bond length is 1.80 Å. The B(3)-B(8) bond length is 1.80 Å. In the fourth B site, B(4) is bonded in a 6-coordinate geometry to one B(10), one B(3), one B(5), one B(6), one B(7), and one B(8) atom. The B(4)-B(10) bond length is 1.83 Å. The B(4)-B(5) bond length is 1.69 Å. The B(4)-B(6) bond length is 1.80 Å. The B(4)-B(7) bond length is 1.80 Å. The B(4)-B(8) bond length is 1.80 Å. In the fifth B site, B(5) is bonded in a 6-coordinate geometry to one B(1), one B(2), one B(4), one B(5), and two equivalent B(9) atoms. The B(5)-B(5) bond length is 1.77 Å. There is one shorter (1.77 Å) and one longer (1.81 Å) B(5)-B(9) bond length. In the sixth B site, B(6) is bonded in a single-bond geometry to one B(10), one B(3), one B(4), one B(7), and one O(1) atom. The B(6)-B(10) bond length is 1.77 Å. The B(6)-B(7) bond length is 1.76 Å. The B(6)-O(1) bond length is 1.48 Å. In the seventh B site, B(7) is bonded in a 6-coordinate geometry to one B(10), one B(11), one B(3), one B(4), one B(6), and one B(8) atom. The B(7)-B(10) bond length is 1.83 Å. The B(7)-B(11) bond length is 1.69 Å. The B(7)-B(8) bond length is 1.76 Å. In the eighth B site, B(8) is bonded in a single-bond geometry to one B(10), one B(3), one B(4), one B(7), and one O(2) atom. The B(8)-B(10) bond length is 1.78 Å. The B(8)-O(2) bond length is 1.48 Å. In the ninth B site, B(9) is bonded in a single-bond geometry to one B(2), two equivalent B(5), and one O(2) atom. The B(9)-O(2) bond length is 1.48 Å. In the tenth B site, B(10) is bonded in a 7-coordinate geometry to one B(10), one B(14), one B(3), one B(4), one B(6), one B(7), and one B(8) atom. The B(10)-B(10) bond length is 2.31 Å. The B(10)-B(14) bond length is 2.31 Å. In the eleventh B site, B(11) is bonded in a 6-coordinate geometry to one B(11), one B(13), one B(14), one B(7), and two equivalent B(12) atoms. The B(11)-B(11) bond length is 1.76 Å. The B(11)-B(13) bond length is 1.80 Å. The B(11)-B(14) bond length is 1.83 Å. Both B(11)-B(12) bond lengths are 1.80 Å. In the twelfth B site, B(12) is bonded in a single-bond geometry to one B(13), one B(14), two equivalent B(11), and one O(2) atom. The B(12)-B(13) bond length is 1.76 Å. The B(12)-B(14) bond length is 1.77 Å. The B(12)-O(2) bond length is 1.48 Å. In the thirteenth B site, B(13) is bonded in a 6-coordinate geometry to one B(13), one B(14), two equivalent B(11), and two equivalent B(12) atoms. The B(13)-B(13) bond length is 1.69 Å. The B(13)-B(14) bond length is 1.83 Å. In the fourteenth B site, B(14) is bonded in a 7-coordinate geometry to one B(13), two equivalent B(10), two equivalent B(11), and two equivalent B(12) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one B(1) and two equivalent B(6) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one B(12), one B(8), and one B(9) atom.