Donor-free 9-aluminafluorenes: molecular structures and reactivity

Area of Science:

• Organometallic Chemistry
• Materials Science
• Organic Synthesis

Background:

• Boron-containing polycyclic aromatic hydrocarbons (PAHs) have diverse applications.
• Aluminum-doped PAHs remain underexplored in scientific literature.
• Developing novel organoaluminum compounds is crucial for materials science.

Purpose of the Study:

• To synthesize and characterize a novel donor-free, sterically unprotected aluminum-doped PAH.
• To investigate the reactivity and structural properties of the synthesized compound.
• To establish a synthetic route to elusive three-coordinate aluminum fluorene derivatives.

Main Methods:

• Synthesis of 9-methyl-9-aluminafluorene (Me-AlFlu) via reaction of 9,9-dimethyl-9-stannafluorene with AlMe3.
• Characterization of the dimer (Me-AlFlu)2 in solid and solution states using crystallographic and spectroscopic methods.
• Reactions of (Me-AlFlu)2 with Lewis bases and Lewis acids to form adducts and new organoaluminum compounds.

Main Results:

• The dimer (Me-AlFlu)2 exhibits dynamic cis/trans interconversion in solution.
• Lewis bases cleave the dimer into monomeric adducts (Me-AlFlu·L).
• Reaction with AlBr3 yields a dimeric bromoaluminofluorene derivative, a precursor to monomeric aluminafluorenes.

Conclusions:

• The study presents the first synthesis of a donor-free, sterically unprotected 9-methyl-9-aluminafluorene.
• The reactivity of the dimer provides access to monomeric aluminafluorene adducts and derivatives.
• This work opens new avenues for exploring aluminum-doped PAHs in catalysis and optoelectronics.