Synthesis and Characterization of Azine Derivatives of Boron

Abstract

Reactions of equimolar amounts of BF₃.2AcOH with azines have resulted in the synthesis of FB(AZ) (where AZ⁻² represents the anion of the azine, AZH₂) type of derivatives. Similar reactions of boric acid dissolved in acetic anhydride or of B(OEt)₃ with such ligands have produced XB(AZ) (where X = OAc or OEt) type of compounds. Spectral assignments and the mode of bonding have been discussed on the basis of electronic, I.R. and ¹H NMR spectral studies. The splitting of √ C=N (∼ 1620 cm⁻¹) and√N-N (1000–900 cm⁻¹) absorptions, each into two bands, indicates the coordination of only one of the two azomethine nitrogens of the ligand to the boron atom. This is further supported by the splitting of the methyl proton signal (2.72 8) of o-hydroxyacetophenoneazine into two signals on chelation with the boron atom. Further, the fluoroboronazinates have been characterized by ¹⁹F N.M.R. spectra and all the complexes were found to be monomers in freezing dioxane.