Synthesis and characterization of amine adducts of tri(4-tolyl)boroxine and tri(3,5-xylyl)boroxine: molecular structure of (4-MeC6H4)3B2O3.cyclohexylamine

Article abstract of DOI:10.1016/0277-5387(95)00130-K

19 1:1 adducts of the triarylboroxines (4-MeC6H4)3B3O3 (PTB) and (3,5-Me2C6H3)3B3O3 (MXB) with N-donor ligands (cyclohexylamine, 4-picoline, 3-picoline, piperidine, morpholine, isobutylamine, dimethylamine, isoquinoline and benzylamine) have been prepared by reaction of stoichiometric quantities of ligand and triarylboroxine in Et2O at room temperature. All 19 adducts have been characterized by elemental analysis, M pt, IR and (1)H and (13)C NMR. C6H11NH2.PTB has been characterized in the solid state by a single-crystal X-ray diffraction study. Solid-state (11)B MAS NMRresults for PTB and its adducts with cyclohexylamine and isoquinoline a re reported. In solution-variable temperature (1)H NMR of the morpholine, cyclohexylamine, isoquinoline and benzylamine adducts of PTB and MXB indicate that a ligand dissociation-recombination process is occuring with ΔG# of ca 43-49 kJ mol**-1.