SYNTHESIS AND STUDY OF MONOMERIC AND DIMERIC BORONATES BY SPECTROSCOPIC METHODS AND X-RAY CRYSTALLOGRAPHY

A series of 2-salicylideneamino ethanol derivatives with substituents in different positions have been brought to reaction with phenylboroni c acid. Depending on the number and position of the substituents in th e ligand, three boronate structure types have been obtained. Thereby, it could be shown that the formation of a macrocyclic dimeric boronate is preferred over the monomeric compound and a [5.4.0]heterobicyclic system with a B(4)-O-B(3) structural unit. The three structure types h ave been analyzed by X-ray crystallography, where a series of paramete rs such as N-->B bond length, torsion angles, tetrahedral character at the boron atom, deviation of the boron atom from the mean plane and s um of bond angles in the heterocyclic rings have been evaluated in ord er to determine the factors for the preferred formation of each compou nd. Finally a new synthetic strategy is presented that permits the syn thesis of other macrocyclic boronates in the future.