2,5-Bis-trimethylsilyl substituted boroles.

Area of Science:

• Organometallic Chemistry
• Materials Science
• Synthetic Chemistry

Background:

• Boroles are heterocyclic compounds containing boron, with applications in materials science.
• Previous studies focused on tetraaryl boroles, often exhibiting blue-green fluorescence.
• Understanding the synthesis and properties of substituted boroles is crucial for developing new functional materials.

Purpose of the Study:

• To synthesize and characterize novel 2,5-disilyl boroles.
• To investigate the spectroscopic and thermal properties of these new compounds.
• To explore synthetic routes and potential challenges in accessing disilyl boroles.

Main Methods:

• Synthesis of 1-Chloro-2,5-(SiMe3)2-3,4-(Ph*)2-borole via reaction of boron trichloride with a dilithiobutadiene precursor.
• Metathesis reactions to introduce aryl groups at the 1-position.
• Spectroscopic analysis (UV-Vis) to determine electronic transitions.
• Thermal stability studies.
• Gutmann-Beckett analysis to assess Lewis acidity.

Main Results:

• Reliable synthesis of 2,5-bis-trimethylsilyl substituted chloroborole in good yield.
• High thermal stability of the chloroborole (up to 130 °C).
• Access to various 1-aryl-2,5-disilyl boroles through metathesis reactions.
• Observation of blue-shifted π/π*-transitions (orange/red color) due to reduced π-system interaction.
• Identification of synthetic challenges, including solvent-dependent selectivity and failure of B/Sn exchange.
• Disilylboroles exhibit reduced Lewis acidity compared to pentaphenyl borole.

Conclusions:

• Novel 2,5-disilyl boroles are accessible through targeted synthesis.
• These compounds possess enhanced thermal stability and distinct photophysical properties compared to tetraaryl boroles.
• Synthetic strategies require careful consideration of reaction conditions and precursors.
• The reduced Lewis acidity suggests potential for unique reactivity and applications.