Boryl Anion: Syntheses and Properties of Novel Borylmetals

This account reviews our recent research on chemistry of “boryl anion”. Boryl anions can be classified with their metallic counterpart, such as Li, Mg, Cu, and Zn in a similar manner to the classification of carbanion. Syntheses and characterizations of boryllithium compounds have been achieved by using bulky substituents to prevent a dimerization of a boryl radical intermediate and nitrogen–containing heterocycle to gain an electronic stabilization. Transmetallation of boryllithium afforded a series of borylmetals having Mg, Zn, Cu, Ag, Au, Ti, or Hf. Some of these borylmetals can be regarded as a boryl anion species possessing a nucleophilic character towards organic electrophiles. Detailed analyses of group 11 borylmetal species showed a strong trans influence of boryl ligand. Borylhafnium complex could be utilized as a catalyst precursor for olefin polymerization.