C-P Bond Cleavage Through Hydrogenation in Ruthenium Complexes Supported by P,N Ligands

Area of Science:

• Organometallic Chemistry
• Catalysis
• Ruthenium Complexes

Background:

• Exploration of ruthenium hydride complexes.
• Synthesis and characterization of novel ligands.

Purpose of the Study:

• Investigate the reactivity of ruthenium hydride complexes supported by pyridine-based ligands.
• Determine the catalytic activity of synthesized complexes in hydrogenation reactions.

Main Methods:

• Synthesis of ruthenium complexes using {Ru(COD)Cl2}.
• Characterization of complexes via spectroscopic methods.
• Density Functional Theory (DFT) calculations for mechanistic insights.
• Catalytic testing in benzaldehyde hydrogenation.

Main Results:

• Formation of [Ru(L1)2(H)Cl] with ligand L1.
• Unexpected C-P bond cleavage and formation of [Ru(L2)(P(H)Bu2)(H)Cl] (2) with ligand L2.
• Identification of intermediate species [Ru(L2)2(H)Cl] (3) and [Ru(L2)2Cl2] (4).
• DFT calculations proposed protonation of carbon as the rate-determining step.
• Complex 2 demonstrated high catalytic activity (TONs up to 44,000) in benzaldehyde hydrogenation.

Conclusions:

• Ruthenium complexes with pyridine-based ligands exhibit diverse reactivity.
• Ligand structure influences reaction pathways, including C-P bond cleavage.
• The synthesized ruthenium hydride complex 2 is a potent catalyst for hydrogenation.