Facile Benzene Reduction by a Ca²⁺ /Al^I Lewis Acid/Base Combination

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Main Group Chemistry

Background:

• Donor-acceptor complexes involving alkali and alkaline earth metals are of significant interest.
• Frustrated Lewis pairs (FLPs) offer unique reactivity pathways for small molecule activation.

Purpose of the Study:

• To synthesize a donor-acceptor complex between a calcium(I) precursor and an aluminum(I) complex.
• To investigate the reactivity of benzene under these conditions.

Main Methods:

• Reaction of a (BDI)Ca⁺ salt with a (BDI)Al^I complex in benzene.
• Characterization of the resulting product using spectroscopic and structural methods (implied).

Main Results:

• Unexpected dearomatization of benzene occurred, forming a puckered C₆H₆^2- ligand.
• A stable (BDI)Ca⁺ (C₆H₆)Al^III(BDI) complex was isolated, featuring an alumina-norbornadiene fragment.
• The complex exhibits stability in solution up to 80°C.

Conclusions:

• Benzene can be activated and incorporated into a complex structure via a likely FLP mechanism.
• This reaction pathway provides a new route to functionalized benzene ligands coordinated to metal centers.
• The findings expand the understanding of main group element reactivity and complex formation.