Electron-Deficient Imidazolium Substituted Cp Ligands and their Ru Complexes

Area of Science:

• Organometallic Chemistry
• Supramolecular Chemistry

Background:

• Cyclopentadienyl (Cp) ligands are fundamental in organometallic chemistry.
• Imidazolium groups are known for their electron-withdrawing properties.

Purpose of the Study:

• To synthesize and characterize novel electron-poor Cp-ylides bearing imidazolium substituents.
• To investigate the electronic properties and reactivity of these new compounds.

Main Methods:

• Synthesis of mono-, di-, and tri(imidazolium)-substituted Cp-ylides.
• Characterization using NMR spectroscopy and X-ray crystallography.
• Electrochemical studies including cyclic voltammetry.
• Density Functional Theory (DFT) calculations.

Main Results:

• Successful synthesis of electron-poor Cp-ylides with varying degrees of imidazolium substitution.
• Formation of monocationic and dicationic ruthenocenes with mono- and di-substituted Cp ligands, respectively.
• Tri-substituted Cp ligands were too electron-poor to form ruthenocenes.
• Ruthenocenes exhibited reversible oxidation, with potentials increasing significantly with each additional imidazolium group (0.53-0.55 V per substituent).
• Reversible oxidation was also observed for the free 1,3-disubstituted ligand.

Conclusions:

• Imidazolium substitution effectively tunes the electronic properties of Cp ligands, making them electron-poor.
• The degree of substitution directly impacts the stability and electrochemical behavior of resulting ruthenocene complexes.
• These findings offer new avenues for designing organometallic compounds with tailored redox properties.