π-Bonding in B–O ring species: Lewis acidity of Me 3B 3O 3, synthesis of amine Me 3B 3O 3 adducts, and the crystal and molecular structure of Me 3B 3O 3.NH 2iBu·MeB(OH) 2

• Published in: Journal of organometallic chemistry Vol. 585; no. 1; pp. 7 - 11
• Main Authors: Beckett, Michael A., Brassington, David S., Owen, Paul, Hursthouse, Michael B., Light, Mark E., Malik, K.M.Abdul, Varma, K.Sukumar
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1999
• Subjects: Boron; Boroxine; Lewis acidity; X-ray structure; Boron; Lewis acidity; Boroxine; X-ray structure
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(99)00182-5

The synthesis and characterisation (m.p., elemental analysis, IR, NMR) of some previously unreported Me 3B 3O 3·L adducts (L=piperidine, isobutylamine, morpholine, 3-picoline, benzylamine) are described. The crystal and molecular structure of Me 3B 3O 3 .NH 2 i Bu·MeB(OH) 2 has been determined by a single-crystal X-ray diffraction study. The structure reveals an unusual H-bond interaction between MeB(OH) 2 and a ring O atom of the six-membered B 3O 3 ring of the trimethylboroxine adduct, Me 3B 3O 3·NH 2 i Bu. The direction of the H-bond strongly suggests sp 2 hybridisation for this O atom. The Lewis acidity of Me 3B 3O 3, Ph 3B 3O 3, 1,3,5-Ph 3B 3N 3Me 3 and 1,3,5-Ph 3C 6H 3 have been estimated by Gutmann’s method and data interpreted in terms of relative π-bonding strength within these ring systems.