Lanthanide polyoxocationic complexes: experimental and theoretical stability studies and Lewis acid catalysis.

Area of Science:

• Inorganic Chemistry
• Catalysis
• Materials Science

Background:

• Polyoxometalates are versatile inorganic clusters with diverse applications.
• Rare-earth metal incorporation into polyoxometalate structures is an active area of research.
• Understanding metal-ligand interactions is crucial for designing functional materials.

Purpose of the Study:

• To synthesize novel polyoxocations incorporating lanthanide ions.
• To investigate the rare-earth metal exchange affinity within the polyoxometalate structure.
• To evaluate the catalytic potential of these new polyoxocations as Lewis acid catalysts.

Main Methods:

• Room temperature synthesis of polyoxocations as chloride salts.
• (31)P NMR spectroscopy for studying rare-earth metal exchange and affinity.
• Density Functional Theory (DFT) calculations for geometric and energetic analysis.
• Catalytic testing of synthesized polyoxocations in Lewis acid-catalyzed reactions.

Main Results:

• Successful synthesis of [ε-PMo(V)(8)Mo(VI)(4)O(36)(OH)(4){Ln(III)(H(2)O)}(4)](5+) (εLn(4)) polyoxocations (Ln=La, Ce, Nd, Sm).
• Demonstrated varying affinities of rare-earth metals for the reduced {ε-PMo(12)} core, with La(III) showing the highest affinity.
• DFT calculations confirmed the coordination preferences and limitations of heavier lanthanides.
• εLn(4) polyoxocations with Ln=La and Ce exhibited efficient Lewis acid catalytic activity.

Conclusions:

• The synthesized εLn(4) polyoxocations represent a new class of efficient Lewis acid catalysts.
• Lanthanum exhibits the strongest affinity for the ε-Keggin polyoxometalate core among the studied rare-earth metals.
• This study is the first to evaluate the catalytic activity of polyoxocations, opening new avenues in catalysis research.