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

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