Borchelate und Bormetallchelate, VI [1] Zur Bildung von Borchelaten aromatischer Azoverbindungen / Boron Chelates and Boron Metal Chelates, VI [1]The Formation of Boron Chelates of Aromatic Azo Compounds

Bidentate chelate reagents incorporating a suitable group (e.g. OH, NH2) in ortho position to the azo-group react with diphenylboronic acid anhydride or boron trihalides (BF3, BCl3) resulting in the BR2-six membered ring-chelates of types 1 and 2. The products of the reaction of tridentate chelate reagents with phenylboronic acid or boron trifluoride at elevated temperature are BR-chelates with two six membered rings (types 3 and 4). The conditions of the formation of the bicyclic chelates 5 and 6 depend on the position of the substituents of the chelate reagents. The incorporation of only one BR2 group is possible if the order of the substituents in 2,2′-dihydroxyazobenzenes is not symmetrical (chelates of the type 7). Structural isomers of boron chelates of the types 5, 6 or 7 with Nα/Nβ isomerism have not yet been observed. The identification of the structures of the above-mentioned complexes was achieved by means of 1H, 11B and 19F NMR and IR spectroscopy. For mass spectrometric analysis see ref. [2].