Stabilization of the Benzene Radical Trianion in an Inverse-Sandwich Yttrium Complex

Area of Science:

• Organometallic Chemistry
• Inorganic Chemistry
• Spectroscopy

Background:

• The chemistry of high oxidation state organic molecules is an area of active research.
• Stabilizing unusual electronic states of aromatic systems presents significant synthetic challenges.

Purpose of the Study:

• To report the first isolation and characterization of the benzene radical trianion.
• To investigate the electronic structure and bonding in this novel species.

Main Methods:

• Synthesis of a yttrium inverse-sandwich complex.
• One-electron chemical reduction using potassium graphite (KC8).
• Characterization via single-crystal X-ray diffraction, EPR, and UV-vis spectroscopy.
• Computational analysis using Density Functional Theory (DFT).

Main Results:

• Successfully synthesized and isolated the benzene radical trianion stabilized by two trivalent yttrium cations.
• Elucidated the molecular structure, confirming strong yttrium-benzene radical interactions.
• Spectroscopic and DFT analyses indicated the unpaired electron spin density resides primarily on the benzene moiety, with weak aromaticity.

Conclusions:

• The benzene radical trianion has been unambiguously synthesized and characterized.
• This work expands the known oxidation states of benzene and provides insights into metal-radical interactions.