Tetracoordinated boronate adducts, bond

Reetz et al. have published a heterotopic receptor, which in addition to a crown ether moiety for complexation of potassium cations, contains a g-bonded Lewis acidic boron center that is able to form a tetracoordinated adduct with anions and with a selectivity for fluoride anions [ref 31]. Novel artificial polytopic receptors for binding of zwitterionic aminocarboxylates have been also published [ref 32]. 

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