AMINE ADDUCTS OF TRIARYLBOROXINES - SYNTHESIS AND CHARACTERIZATION OFADDUCTS OF TRI(2-TOLYL)BOROXINE AND CRYSTAL-STRUCTURES OF (4-MEC6H4)(3)B3O3 AND (4-MEC6H4)(3)B3O3.4-PICOLINE

Seven 1:1 adducts of the triarylboroxine (2-MeC6H4)(3)B3O3 with N-dono r ligands (4-picoline, cyclohexylamine, pyridine, S-picoline, piperidi ne, isoquinoline, benzylamine) have been prepared by reaction of equim olar quantities of amine and (2-MeC6H4)(3)B3O3 in Et2O at room tempera ture. These adducts have been characterized by elemental analysis, mel ting point, IR spectroscopy and by H-1 and C-13 NMR spectroscopy. Room temperature solution H-1 NMR spectra of these complexes suggest that rapid ligand dissociation-recombination exchange processes are occurri ng. The related compounds (4-MeC6H4)(3)B3O3 and (4-MeC6H4)(3)B3O3 . 4- picoline have been characterized in the solid state by single crystal X-ray diffraction studies. Solid state B-11 MAS NMR results are report ed for triarylboroxines (4-MeC6H4)(3)B3O3 and (3,5-Me2C6H3)(3)B3O3 and for the amine adducts (4-MeC6H4)(3)B3O3 . cyclohexylamine, (4-MeC6H4) (3)B3O3 . isoquinoline, (4-MeC6H4)(3)B3O3 . benzylamine, (3,5-Me2C6H3) (3)B3O3 . 4-picoline and (3,5-Me2C6H3)(3)B3O3 . morpholine. (C) 1997 E lsevier Science S.A.