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Updated: Sep 1, 2025
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Published on: May 11, 2017
Formation of a Strong Heterogeneous Aluminum Lewis Acid on Silica
Kavyasripriya K Samudrala1, Winn Huynh1, Rick W Dorn2,3
1Department of Chemistry, University of California, Riverside, Riverside, CA 92521, USA.
Abstract:
Al(OC(CF3 )3 )(PhF) reacts with silanols present on partially dehydroxylated silica to form well-defined ≡SiOAl(OC(CF3 )3 )2 (O(Si≡)2 ) (1). 27 Al NMR and DFT calculations with a small cluster model to approximate the silica surface show that the aluminum in 1 adopts a distorted trigonal bipyramidal coordination geometry by coordinating to a nearby siloxane bridge and a fluorine from the alkoxide. Fluoride ion affinity (FIA) calculations follow experimental trends and show that 1 is a stronger Lewis acid than B(C6 F5 )3 and Al(OC(CF3 )3 )(PhF) but is weaker than Al(OC(CF3 )3 ) and i Pr3 Si+ . Cp2 Zr(CH3 )2 reacts with 1 to form [Cp2 ZrCH3 ][≡SiOAl(OC(CF3 )3 )2 (CH3 )] (3) by methide abstraction. This reactivity pattern is similar to reactions of organometallics with the proposed strong Lewis acid sites present on Al2 O3 .
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