Inorganic Chemistry, Vol.59, No.8, 5558-5563, 2020
Tridentate Ligand with Three Carbanions as Donor Atoms: Formation of Dinuclear, Heptacyclic Complexes of Boron, Aluminum, or Gallium with B-C-B, Al-C-Al, or Ga-C-Ga Three-Center-Two-Electron Bonds
The trilithium compound 1,3-[PhMe2Si-C(Li)=C(H)](2)C6H3Li (2b) reacted with BCl3, AlCl3, or GaCl3 by salt elimination to yield dinuclear heptacyclic compounds (4). Two tridentate tricarbanionic ligands coordinate two B, Al, or Ga atoms and adopt a helical arrangement of the ligands around a central E-2 unit. The unusual structures comprise E2C2 heterocycles with two 3c-2e (three-center-two-electron) E-C-E bonds and two C atoms of aromatic rings in the bridging positions. While such a bonding situation is well-documented in AI chemistry, it is rare for B and Ga compounds. Insight into the bonding situation of the molecules is provided by DFT calculations.