[4-(Ph₃ B)-2,6-Mes₂ Py]^- : A Sterically Demanding Anionic Pyridine

Area of Science:

• Organic Chemistry
• Coordination Chemistry
• Supramolecular Chemistry

Background:

• Sterically hindered pyridines are important in catalysis and coordination chemistry.
• Introducing electron-donating groups can increase pyridine basicity.
• Anionic pyridines offer unique reactivity profiles.

Purpose of the Study:

• To synthesize and characterize a sterically demanding anionic pyridine with a triphenylborate group.
• To investigate the enhanced basicity and nucleophilicity of the novel pyridine derivative.
• To explore its potential as a ligand in coordination chemistry.

Main Methods:

• Synthesis of 2,6-dimesitylpyridine functionalized with a triphenylborate group.
• Determination of pKa value via potentiometric titration.
• Reactions with TMSCl and Li[BH4] to assess nucleophilicity and ligand properties.
• X-ray crystallography for structural elucidation.

Main Results:

• The synthesized anionic pyridine possesses a high pKa of 18.46, exceeding that of 4-dimethylaminopyridine.
• Demonstrated high nucleophilicity through THF ring-opening reaction with its lithium salt.
• Formation of a Lewis acid/base adduct with Li[BH4], indicating its utility as a monodentate ligand.
• Crystal structures of synthesized compounds were determined.

Conclusions:

• The triphenylborate group significantly enhances the basicity and nucleophilicity of the sterically hindered pyridine.
• The compound serves as an effective monodentate ligand in coordination chemistry.
• The orthogonal orientation of mesityl groups preserves nitrogen accessibility.