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π-Bonding in B–O ring species: Lewis acidity of Me3B3O3, synthesis of amine Me3B3O3 adducts, and the crystal and molecular structure of Me3B3O3.NH2iBu·MeB(OH)2

1999; Elsevier BV; Volume: 585; Issue: 1 Linguagem: Inglês

10.1016/s0022-328x(99)00182-5

1872-8561

Michael A. Beckett, D.S. Brassington, Paul Owen, Michael B. Hursthouse, Mark E. Light, K. M. Abdul Malik, K. Sukumar Varma,

Synthesis and characterization of novel inorganic/organometallic compounds

The synthesis and characterisation (m.p., elemental analysis, IR, NMR) of some previously unreported Me3B3O3·L adducts (L=piperidine, isobutylamine, morpholine, 3-picoline, benzylamine) are described. The crystal and molecular structure of Me3B3O3.NH2iBu·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 B3O3 ring of the trimethylboroxine adduct, Me3B3O3·NH2iBu. The direction of the H-bond strongly suggests sp2 hybridisation for this O atom. The Lewis acidity of Me3B3O3, Ph3B3O3, 1,3,5-Ph3B3N3Me3 and 1,3,5-Ph3C6H3 have been estimated by Gutmann's method and data interpreted in terms of relative π-bonding strength within these ring systems.