Probing the Boundaries between Lewis-Basic and Redox Behavior of a Parent Borylene

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry

Background:

• Borylenes are versatile compounds with unique electronic properties.
• Group 13 elements (B, Al, Ga, In) and their halides offer diverse reactivity patterns.

Purpose of the Study:

• To investigate the Lewis basicity and reducing capabilities of a parent borylene, (CAAC)(Me3P)BH.
• To explore the reactions of this borylene with group 13 trichlorides and boron trihalides.
• To elucidate the influence of group 13 element and halide identity on reaction pathways.

Main Methods:

• Synthesis and characterization of borylene adducts.
• Spectroscopic analysis to identify reaction products.
• Computational calculations to determine electronic structures and bond energies.

Main Results:

• The borylene acts as both a Lewis base and a one-electron reducing agent towards ECl3 (E=B, Al, Ga, In).
• Adduct formation (1-ECl3) and radical cation ([1]•+) generation were observed, with increased radical cation character for heavier group 13 elements.
• Reactions with BX3 (X=F, Cl, Br, I) led to sequential adduct formation, halide abstraction, and borylboronium cation formation.
• A trend towards redox processes was noted with heavier halides.
• Calculations confirmed strong Lewis basicity and increasing B-E bond dissociation energies down group 13 and the halide group.

Conclusions:

• The parent borylene exhibits dual Lewis base and reducing agent behavior.
• Reactivity is modulated by the nature of the group 13 element and the halide.
• Computational data supports the experimental observations regarding Lewis acidity and bond strengths.