Mono- and diboronates derived from tridentate ONO ligands and arylboronic acids

The syntheses of eight [4.3.0] heterobicyclic boronates containing a N → B coordinative bond are described. The monomeric compounds were prepared by reaction of arylboronic acids with a tridentate ligand having the ONO donor set of atoms. It was shown that substituents at the para-position of the B-phenyl moiety transmit electronic effects to the CN bond which in turn is polarized by formation of the N → B coordination bond. At the same time, related tridentate ligands were also reacted with 1,4-benzenediboronic acid in order to prepare benzene diboron complexes. The structure of this type of compounds was confirmed by X-ray analysis for one of the derivatives.

Graphical abstractThe synthesis and characterization of eight monomeric boron complexes is described (A). In these compounds, the presence of donor or acceptor groups in the para-position of the B-phenyl group has an electronic effect on the CN moiety, which was determined by the linear correlation observed in a graph of 1H NMR chemical shifts for the C(H)N group versus σ Hammett values. Furthermore, in the diboronates complexes like B, polarization on the CN moiety is increased.Figure optionsDownload full-size imageDownload as PowerPoint slide