B8O crystallizes in the monoclinic P2_1/m space group. There are sixteen inequivalent B sites. In the first B site, B(1) is bonded in a 6-coordinate geometry to one B(1), one B(10), one B(11), one B(14), one B(6), and one B(8) atom. In the second B site, B(2) is bonded in a 7-coordinate geometry to one B(15), one B(2), one B(3), one B(4), one B(6), one B(7), and one B(9) atom. In the third B site, B(3) is bonded in a single-bond geometry to one B(2), one B(4), one B(5), one B(6), and one O(1) atom. In the fourth B site, B(4) is bonded in a 6-coordinate geometry to one B(15), one B(2), one B(3), one B(5), and two equivalent B(4) atoms. In the fifth B site, B(5) is bonded in a 6-coordinate geometry to one B(14), one B(16), two equivalent B(3), and two equivalent B(4) atoms. In the sixth B site, B(6) is bonded in a 6-coordinate geometry to one B(1), one B(16), one B(2), one B(3), one B(6), and one B(7) atom. In the seventh B site, B(7) is bonded in a 6-coordinate geometry to one B(13), one B(15), two equivalent B(2), and two equivalent B(6) atoms. In the eighth B site, B(8) is bonded in a single-bond geometry to one B(1), one B(12), one B(14), one B(9), and one O(2) atom. In the ninth B site, B(9) is bonded in a 7-coordinate geometry to one B(14), two equivalent B(12), two equivalent B(2), and two equivalent B(8) atoms. In the tenth B site, B(10) is bonded in a single-bond geometry to one B(13), two equivalent B(1), and one O(3) atom. In the eleventh B site, B(11) is bonded in a single-bond geometry to one B(1), one B(12), one B(13), and one O(3) atom. In the twelfth B site, B(12) is bonded in a 6-coordinate geometry to one B(11), one B(13), one B(8), one B(9), and two equivalent B(12) atoms. In the thirteenth B site, B(13) is bonded in a 6-coordinate geometry to one B(10), one B(7), two equivalent B(11), and two equivalent B(12) atoms. In the fourteenth B site, B(14) is bonded in a 6-coordinate geometry to one B(5), one B(9), two equivalent B(1), and two equivalent B(8) atoms. In the fifteenth B site, B(15) is bonded in a single-bond geometry to one B(7), two equivalent B(2), two equivalent B(4), and one O(2) atom. In the sixteenth B site, B(16) is bonded in a single-bond geometry to one B(5), two equivalent B(6), and one O(1) atom. There are three inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one B(16) and two equivalent B(3) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one B(15) and two equivalent B(8) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one B(10) and two equivalent B(11) atoms.
B8O crystallizes in the monoclinic P2_1/m space group. There are sixteen inequivalent B sites. In the first B site, B(1) is bonded in a 6-coordinate geometry to one B(1), one B(10), one B(11), one B(14), one B(6), and one B(8) atom. The B(1)-B(1) bond length is 1.77 Å. The B(1)-B(10) bond length is 1.77 Å. The B(1)-B(11) bond length is 1.80 Å. The B(1)-B(14) bond length is 1.79 Å. The B(1)-B(6) bond length is 1.70 Å. The B(1)-B(8) bond length is 1.77 Å. In the second B site, B(2) is bonded in a 7-coordinate geometry to one B(15), one B(2), one B(3), one B(4), one B(6), one B(7), and one B(9) atom. The B(2)-B(15) bond length is 1.78 Å. The B(2)-B(2) bond length is 2.33 Å. The B(2)-B(3) bond length is 1.78 Å. The B(2)-B(4) bond length is 1.82 Å. The B(2)-B(6) bond length is 1.83 Å. The B(2)-B(7) bond length is 1.85 Å. The B(2)-B(9) bond length is 2.22 Å. In the third B site, B(3) is bonded in a single-bond geometry to one B(2), one B(4), one B(5), one B(6), and one O(1) atom. The B(3)-B(4) bond length is 1.76 Å. The B(3)-B(5) bond length is 1.78 Å. The B(3)-B(6) bond length is 1.81 Å. The B(3)-O(1) bond length is 1.48 Å. In the fourth B site, B(4) is bonded in a 6-coordinate geometry to one B(15), one B(2), one B(3), one B(5), and two equivalent B(4) atoms. The B(4)-B(15) bond length is 1.76 Å. The B(4)-B(5) bond length is 1.77 Å. There is one shorter (1.69 Å) and one longer (1.80 Å) B(4)-B(4) bond length. In the fifth B site, B(5) is bonded in a 6-coordinate geometry to one B(14), one B(16), two equivalent B(3), and two equivalent B(4) atoms. The B(5)-B(14) bond length is 1.69 Å. The B(5)-B(16) bond length is 1.80 Å. In the sixth B site, B(6) is bonded in a 6-coordinate geometry to one B(1), one B(16), one B(2), one B(3), one B(6), and one B(7) atom. The B(6)-B(16) bond length is 1.79 Å. The B(6)-B(6) bond length is 1.80 Å. The B(6)-B(7) bond length is 1.78 Å. In the seventh B site, B(7) is bonded in a 6-coordinate geometry to one B(13), one B(15), two equivalent B(2), and two equivalent B(6) atoms. The B(7)-B(13) bond length is 1.69 Å. The B(7)-B(15) bond length is 1.80 Å. In the eighth B site, B(8) is bonded in a single-bond geometry to one B(1), one B(12), one B(14), one B(9), and one O(2) atom. The B(8)-B(12) bond length is 1.81 Å. The B(8)-B(14) bond length is 1.76 Å. The B(8)-B(9) bond length is 1.79 Å. The B(8)-O(2) bond length is 1.47 Å. In the ninth B site, B(9) is bonded in a 7-coordinate geometry to one B(14), two equivalent B(12), two equivalent B(2), and two equivalent B(8) atoms. The B(9)-B(14) bond length is 1.85 Å. Both B(9)-B(12) bond lengths are 1.85 Å. In the tenth B site, B(10) is bonded in a single-bond geometry to one B(13), two equivalent B(1), and one O(3) atom. The B(10)-B(13) bond length is 1.81 Å. The B(10)-O(3) bond length is 1.49 Å. In the eleventh B site, B(11) is bonded in a single-bond geometry to one B(1), one B(12), one B(13), and one O(3) atom. The B(11)-B(12) bond length is 1.79 Å. The B(11)-B(13) bond length is 1.76 Å. The B(11)-O(3) bond length is 1.49 Å. In the twelfth B site, B(12) is bonded in a 6-coordinate geometry to one B(11), one B(13), one B(8), one B(9), and two equivalent B(12) atoms. The B(12)-B(13) bond length is 1.77 Å. There is one shorter (1.69 Å) and one longer (1.75 Å) B(12)-B(12) bond length. In the thirteenth B site, B(13) is bonded in a 6-coordinate geometry to one B(10), one B(7), two equivalent B(11), and two equivalent B(12) atoms. In the fourteenth B site, B(14) is bonded in a 6-coordinate geometry to one B(5), one B(9), two equivalent B(1), and two equivalent B(8) atoms. In the fifteenth B site, B(15) is bonded in a single-bond geometry to one B(7), two equivalent B(2), two equivalent B(4), and one O(2) atom. The B(15)-O(2) bond length is 1.46 Å. In the sixteenth B site, B(16) is bonded in a single-bond geometry to one B(5), two equivalent B(6), and one O(1) atom. The B(16)-O(1) bond length is 1.49 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one B(16) and two equivalent B(3) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one B(15) and two equivalent B(8) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one B(10) and two equivalent B(11) atoms.