Nature of intramolecular transannular interaction in group 13 atranes: a theoretical study

Ab initio molecular orbital (MO) calculations at the MP2/6-31+G* level coupled with quantum theory of atoms in molecules (QTAIM) analysis were carried out on group 13 atranes (M = B, Al, Ga) with special emphasis on the nature of the transannular M···N interaction present in these molecules. Substituents at the equatorial position were found to influence the extent of transannular interaction. Boratrane molecules were found to have the strongest M···N interaction and consequently have higher stabilization energies. QTAIM analysis revealed the presence of significant covalent character in the transannular M···N bonds which decreases down the group.