A Neutral Borylene and its Conversion to a Radical by Selective Hydrogen Transfer

Area of Science:

• Organometallic Chemistry
• Boron Chemistry
• Radical Chemistry

Background:

• Low-valent boron compounds are of significant interest due to their unique electronic properties and reactivity.
• Stabilization of low-valent boron species often requires sophisticated ligand design.

Purpose of the Study:

• To synthesize and characterize novel low-valent boron compounds using a hybrid ligand system.
• To investigate the reactivity of these compounds, particularly in hydrogen abstraction.

Main Methods:

• Selective reduction of dihaloboranes (X2B-Tip) using KC8 and Mg metal.
• Characterization of the resulting boryl radical and neutral borylene complexes.
• Reaction of the neutral borylene with 1,4-cyclohexadiene.
• Quantum chemical studies to elucidate electronic structures and bonding.

Main Results:

• Successful synthesis of a stable boryl radical [C6H4(PPh2)LSiBTip][Br] (1) and a neutral borylene [C6H4(PPh2)LSiBTip] (2).
• Compound 2 undergoes hydrogen abstraction with 1,4-cyclohexadiene to form radical [C6H4(PPh2)LSiB(H)Tip] (3).
• Quantum chemical analysis confirmed the nature of the radical and borylene species, highlighting stabilization through hyperconjugation and π-conjugation.

Conclusions:

• The hybrid ligand enables the isolation of stable low-valent boron species, a boryl radical and a neutral borylene.
• These compounds exhibit high hydrogen abstraction energy and basicity, respectively.
• The study provides insights into the stabilization and reactivity of low-valent boron compounds.