Synthesis, characterization and X-ray studies of new six–seven membered rings [4.5.0] heterobicyclic system of monomeric boronates

Different tridentate ligands derived from ethanolamines and 2-hydroxyacetophenone, 2-hydroxybenzophenone and salicylaldehyde were reacted with two equivalents of phenylboronic acid to obtain compounds 6a–6f which are [4.5.0] heterobicyclic systems with a B−O−B structural unit. The boronates were fully characterized and two heterobicyclic [4.5.0] structures have been analyzed by X-ray crystallography, where a series of parameters such as bond distances, bond angles, torsion angles, tetrahedral character at the boron atom and deviation of the boron atom from the mean plane have been evaluated.