Abstract
The azaβclosoβboranes ArNB~9~H~9~ (1, Ar = pβClC~6~H~4~) and MeNB~11~H~11~ (2) were brominated, iodinated, or methylated under FriedelβCrafts conditions to give ArNB~9~H~4~Br~5~ (3), ArNB~9~H~7~I~2~ (4), ArNB~9~H~4~Me~5~ (7), MeNB~11~H~10~Br (5), MeNB~11~H~10~I (6), and MeNB~11~H~5~Me~6~ (9), respectively. The upper boron belt adjacent to nitrogen is not involved in the substitution reactions with 1 and 2. The antipodal position and the lower belt are attacked by electrophiles in the case of 1; the antipodal position is the preferred one in the case of 2. By prolongated action of triflic acid on the methylated species 7 and 9, one methyl group is replaced by the triflate group to give ArNB~9~H~4~Me~4~(OTrf) (8) and MeNB~11~H~5~Me~5~β(OTrf) (10) with this group in the positions 6 and 12, respectively. The NMR data indicate the cluster symmetries C~s~ (4, 8), C~4v~ (3, 7), and C~5v~ (5, 6, 9, 10). Crystal structure investigations of 5 (space group Cc) and 10 (space group C2/c) showed that the molecular dimensions of the NB~11~ skeleton are comparable to those of closo, β(PhCH~2~)NB~11~H~11~.