Borinine (Borabenzene): Its Structure and Vibrational Spectrum. A Quantumchemical Study

Abstract

Recently we reported the results of some semiempirical and ab initio studies in which we compared the electronic structure of the hitherto unknown borinine with those of benzene and pyridine. The results of our calculations led us to the conclusion that the elusive nature of borabenzene is caused by its high reactivity, which might at least in part be due to the pronounced σ acceptor properties of a low-lying σ* molecular orbital. We now present the results of further ab initio and semiempirical (MNDO) investigations in which we performed full geometry optimizations for the molecule using two different basis sets (STO-3G, 4-31G) and also calculated the vibrational spectra of the 10 B and 11 B isotopomeric borabenzene molecules at the 4-31 G level of ab initio theory and with the semiempirical MNDO method. The calculated vibrational spectrum might be helpful to the experimentalist in identifying the molecule, for example trapped in a rare gas matrix among the side products. The calculated orbital energies can be useful in identifying the molecule by means of its photoelectron spectrum.