Study of the reaction of tridentate ligands with ferrocenyl boronic acid

Evaluation of the reactivity of eight tridentate ligands derived from amino alcohols and salicylaldehyde, 2-hydroxyacetophenone, or 2-hydroxybenzophenone with ferrocenyl boronic acid has shown that the reaction leads to both monomeric and dimeric ferrocenyl boronates. A coordinative N-B bond is essential to give the tetrahedral boron atoms that are responsible for the formation of heterobicyclic structures containing six, seven and ten members. The purity and identity of all compounds were unequivocally established by analytical and multinuclear (H-1, B-11, C-13) magnetic resonance spectroscopic data. Furthermore, the structures of the dimeric (2a) and monomeric (5b) boron complexes were established by X-ray diffraction analyses. The dimeric compound contains a ten-membered ring in a boat-chair-boat conformation, while the monomeric compound has a seven-membered ring with a chair conformation. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.