AI Article Synopsis
- - The doubly protonated Lindqvist-type niobium oxide cluster [H(NbO)], created using microwave-assisted hydrothermal synthesis, acts as a superbase catalyst for Knoevenagel and crossed aldol condensation reactions, with high pK values indicating strong basicity.
- - Uniquely, [H(NbO)] retains its superbase capabilities even in the presence of water, contrary to typical expectations that water diminishes the basicity of metal oxides and organic superbases.
- - Density functional theory calculations suggest that the basicity of [H(NbO)] is maintained due to negatively charged surface oxygens that remain even after proton adsorption, along with the presence of un-protonated basic sites
Article Abstract
Here, doubly protonated Lindqvist-type niobium oxide cluster [H(NbO)], fabricated by microwave-assisted hydrothermal synthesis, exhibited superbase catalysis for Knoevenagel and crossed aldol condensation reactions accompanied by activating C-H bond with pK >26 and proton abstraction from a base indicator with pK=26.5. Surprisingly, [H(NbO)] exhibited water-tolerant superbase properties for Knoevenagel and crossed aldol condensation reactions in the presence of water, although it is well known that the strong basicity of metal oxides and organic superbase is typically lost by the adsorption of water. Density functional theory calculation revealed that the basic surface oxygens that share the corner of NbO units in [H(NbO)] maintained the negative charges even after proton adsorption. This proton capacity and the presence of un-protonated basic sites led to the water tolerance of the superbase catalysis.
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| http://dx.doi.org/10.1002/anie.202401526 | DOI Listing |
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Water-Tolerant Superbase Polyoxometalate [H(NbO)] for Homogeneous Catalysis.
Angew Chem Int Ed Engl
April 2024
Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan.
Article Synopsis
- - The doubly protonated Lindqvist-type niobium oxide cluster [H(NbO)], created using microwave-assisted hydrothermal synthesis, acts as a superbase catalyst for Knoevenagel and crossed aldol condensation reactions, with high pK values indicating strong basicity.
- - Uniquely, [H(NbO)] retains its superbase capabilities even in the presence of water, contrary to typical expectations that water diminishes the basicity of metal oxides and organic superbases.
- - Density functional theory calculations suggest that the basicity of [H(NbO)] is maintained due to negatively charged surface oxygens that remain even after proton adsorption, along with the presence of un-protonated basic sites
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