Nuclear magnetic resonance studies of boron compounds : XVI. Carbon-13 studies of organoboranes: Phenylboranes and boron-substituted aromatic heterocycles

¹³C and ¹¹B NMR data of 29 phenylboranes and 9 boron-substituted aromatic heterocycles (thiophene, N-methylpyrrole and furan) are discussed. The observed ¹³C chemical shifts of the para-carbon atoms in phenylboranes and the corresponding carbon atoms in the aromatic heterocycles are consistent with mesomeric interactions of the boryl group with the aromatic system. The trend of δ(¹³C(para)) in phenylboranes corresponds to that observed for isoelectronic phenylcarbocations. Low temperature ¹³C NMR and/or ¹³C {¹¹B, ¹H} heterocuclear triple resonance experiments were employed to obtain the ¹³C chemical shifts of the boron-bonded carbon atoms.