Can triorganoboroxins exist in a "monomeric" R-B=O form? MNDO calculations and ebulliometric molecular weight determination

Article abstract of DOI:10.1016/0022-328X(94)80145-2

MNDO calculations were made for triethylboroxin (EtBO)3 and triphenylboroxin (PhBO)3 using both X-ray determined and optimized geometry of these molecules.The results were compared with hypothetical "monomeric" molecules R-B-O.Calculated energies of trimerization are about -200 kJ mol^-1 for both compounds and confirm the much higher stability of the "trimer".Ebulliometric determination of molecular weight of triphenylboroxin in 2-pentanone confirms its trimeric character. Key words: Boroxin; MNDO calculations