Phosphines on Colloidal Nickel Nanocatalysts to Lower the Onset Temperature of Terminal Alkynes Hydrogenation
Résumé
Catalysis by colloidal suspensions of metal nanoparticles (NPs) is becoming more and more conceptual value because the hydrogenation may have been driven by the frustrated Lewis pair (FLP) between the Lewis basic phosphine and the Lewis acid nickel surface, forming a so-called "NanoFLP". We investigated this proposal using 10 phosphines and used a stereoelectronic map to rationalize their ability to boost the conversion, showing that moderately hindered and fairly donating phosphines are most adequate. Moreover, we demonstrated that less than 2 phosphines per Ni surface atom are enough for the effect to arise. We showed that other terminal alkynes like 1-octyne can be hydrogenated with this method. Lastly, comparison of conversion for 5 para-substituted phenylacetylenes was used to discuss the effects of electronic donation and steric hindrance at the surface active site.
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