The Radicals cAAC^Me·AlR₂(thf) (R = Me, Et) as Synthons for Aluminum(II)-Centered Radicals AlR₂

Area of Science:

• Organometallic Chemistry
• Radical Chemistry
• Carbene Chemistry

Background:

• Cyclic (alkyl)(amino)carbenes (cAACs) are versatile ligands in main group chemistry.
• Aluminum(II) species are relatively underexplored compared to other oxidation states.
• Persistent radicals offer unique opportunities in synthesis and catalysis.

Purpose of the Study:

• To synthesize and characterize novel aluminum(II)-centered radicals.
• To investigate the electronic structure and stability of these radical species.
• To explore the reactivity of aluminum(II) radicals derived from cAAC ligands.

Main Methods:

• Synthesis of iodoalane precursors (cAAC·AlR2I).
• Preparation and characterization of aluminyl radicals (cAAC·AlR2(thf)) using EPR spectroscopy and single-crystal X-ray diffraction (SC-XRD).
• Computational studies using Density Functional Theory (DFT) to understand radical character and ligand dissociation.

Main Results:

• The successful synthesis of two new aluminum(II)-centered radicals, cAAC·AlMe2(thf) and cAAC·AlEt2(thf).
• EPR and SC-XRD data, supported by DFT calculations, confirmed the radicals are primarily cAAC-centered.
• These compounds represent rare examples of persistent aluminum(II)-centered radicals and synthons.

Conclusions:

• The synthesized compounds are stable, persistent aluminum(II)-centered radicals.
• The dissociation of the thf ligand is a crucial step in their reactivity.
• These findings open avenues for utilizing aluminum(II) radicals in novel chemical transformations.