抄録
In this contribution, the chemistry of borane ligands acting as sigma electron acceptors has been reviewed briefly. Borane works as a Lewis acid by its empty p orbital, and can withdraw the electron density from the transition metal through the s interaction between d orbital of transition metal and p orbital of borane. This class of borane ligand is referred to Z-type ligand, which should have a fascinating property to tune the electron density of the metal center. Recently, Peters and his co-worker have made significant contribution to the chemistry of Z-type ligand. They have isolated the series of iron complexes with the TPB ligand that span four different electronic states ranging from (Fe-B)6 to (Fe-B)9. Achievement of syntheses of these (TPB)Fe complexes having various electron configurations likely results from the ability of the Fe→B interaction to respond to changes in the electronic properties of the metal center.
