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Increased Lewis acidity in hafnium-substituted polyoxotungstates
Cécile Boglio1, Kevin Micoine, Pauline Rémy
1Université Pierre et Marie Curie-Paris 6, Laboratoire de chimie organique (UMR CNRS 7611), Institut de chimie moléculaire (FR 2769), C. 229, 4 place Jussieu, 75005 Paris, France.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|March 17, 2007
Summary
New hafnium-substituted polyoxotungstates exhibit enhanced Lewis acidity, enabling challenging organic reactions like those involving aldehydes. These tunable catalysts are recoverable and reusable, offering a greener approach to synthesis.
Area of Science:
- Inorganic Chemistry
- Catalysis
- Materials Science
Background:
- Polyoxotungstates are versatile inorganic clusters with tunable properties.
- Lewis acids are crucial catalysts in organic synthesis.
- Previous polyoxotungstates showed limitations in catalyzing certain reactions.
Purpose of the Study:
- To synthesize novel polyoxotungstates incorporating hafnium.
- To evaluate the Lewis acidity and catalytic activity of these new compounds.
- To explore their application in challenging organic transformations.
Main Methods:
- Reaction of monolacunary polyoxotungstates with HfCl(4).
- Isolation of products as organo-soluble tetrabutylammonium (TBA) salts.
- Characterization using mass spectrometry and catalytic activity assessment.
Main Results:
- Synthesis of [alpha(1)-HfP(2)W(17)O(61)](6-) and [alpha-Hf(OH)PW(11)O(39)](4-) as TBA salts.
- Demonstrated enhanced Lewis acidity compared to known lanthanide analogs.
- Successful catalysis of Mukaiyama aldol and Mannich-type additions, including reactions with aldehydes.
Conclusions:
- Hafnium incorporation fine-tunes Lewis acidity in polyoxotungstates.
- These novel catalysts enable previously difficult organic reactions.
- The catalysts are easily recoverable and reusable, promoting sustainable chemistry.
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