Exceptionally facile CO addition to a saturated ruthenium complex.

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Catalysis

Background:

• The reactivity of ruthenium complexes is crucial in catalysis.
• Understanding ligand effects on metal center reactivity is key.
• Cp* and cymene ligands offer distinct electronic and steric environments.

Purpose of the Study:

• To synthesize and characterize a novel Cp* ruthenium complex.
• To investigate the reactivity of this complex towards carbon monoxide (CO).
• To compare its reactivity with a related cymene ruthenium complex and elucidate the underlying mechanism.

Main Methods:

• Synthesis and full characterization of the target ruthenium complex.
• Reactivity studies involving carbon monoxide addition.
• X-ray crystallography for structural determination.
• Density Functional Theory (DFT) calculations for mechanistic insights.

Main Results:

• The Cp* ruthenium complex, Cp*Ru[eta3-HC(PPh2NPh)2], exhibits a piano stool structure.
• This complex rapidly reacts with CO, displacing a ligand nitrogen atom.
• The analogous cymene complex does not react with CO under identical conditions.
• DFT calculations identified a low-energy intermediate and revealed thermodynamic origins for the reactivity difference.

Conclusions:

• The Cp* ligand significantly enhances the reactivity of the ruthenium center towards CO compared to the cymene ligand.
• Thermodynamic factors, specifically the energy change for CO binding, dictate the observed reactivity.
• The study provides insights into ligand design for tuning organometallic reactivity.