Anionic Boraza-Crown Ethers

Making one out of two : Dimeric boraza-crown ethers bridge the gap between metallacrowns and aza-crown ethers with a strikingly simple synthesis. Dioxazaborocanes react with alkoxides to form the corresponding anionic boronates, which combine to form dimers upon ring-opening reactions. The presence of the dimers was proven in the solid state and in solution by X-ray crystallography and NMR spectroscopy, respectively. The influence of the sodium and potassium ions on the stability of boraza-crown ethers was examined using DFT calculations. The dissociation of the dimers to the monomeric species was found to be endothermic, independently of the counterion. Finally, their ability to engage in cross-coupling reactions was validated for two different compounds.