Ligand-Functionalized Organometallic Polyoxometalate as an Efficient Catalyst Precursor for Amide Hydrogenation

Area of Science:

• Heterogeneous catalysis
• Organometallic chemistry
• Polyoxometalate chemistry

Background:

• Amide hydrogenation is crucial for amine synthesis.
• Efficient heterogeneous catalysts require synergistic bimetallic active sites.
• Developing new catalyst precursors is key to improving hydrogenation processes.

Purpose of the Study:

• To synthesize a novel Rh-Mo organometallic polyoxometalate as a catalyst precursor for amide hydrogenation.
• To investigate the structure-activity relationship of different Rh-Mo precursors.
• To evaluate the performance of the synthesized catalyst for various amide types under mild conditions.

Main Methods:

• Synthesis of [(RhCp^E)₄Mo₄O₁₆] organometallic polyoxometalate.
• Preparation and characterization of supported Rh-Mo catalysts.
• Amide hydrogenation reactions under varying conditions (0.8 MPa H₂, 353–393 K).
• Analysis of catalyst activity, selectivity, and dispersibility.

Main Results:

• The [(RhCp^E)₄Mo₄O₁₆] precursor yielded the most active Rh-Mo catalyst for amide hydrogenation.
• The catalyst effectively hydrogenated primary, secondary, and tertiary amides with high conversion (97%) and selectivity (76%) for primary amides.
• Ethoxycarbonyl ligands (Cp^E) facilitated electrostatic interactions with Al₂O₃ support, enhancing catalyst dispersibility.

Conclusions:

• [(RhCp^E)₄Mo₄O₁₆] is a highly effective precursor for Rh-Mo catalysts in amide hydrogenation.
• The synergy between Rh/Mo interfacial active sites and ligand-support interactions drives catalyst efficiency.
• This approach offers a promising route for developing advanced heterogeneous catalysts for amine production.