Differences in the Reactivity of Geminal Si−O−P and Al−O−P Frustrated Lewis Pairs
Lucas Wickemeyer, Lukas Hartmann, Beate Neumann, Hans‐Georg Stammler, Norbert W. Mitzel
Abstract
Abstract The new oxygen‐bridged geminal Si/P Frustrated Lewis Pair (FLP) t Bu 2 P−O−Si(C 2 F 5 ) 3 ( 2 ) is able to reversibly bind carbon dioxide at ambient temperature. We compared its reactivity towards benzil, but‐3‐en‐2‐one, nitriles and phenylacetylene to that of the Al/P FLP t Bu 2 P−O−AlBis 2 (Bis=−CH(SiMe 3 ) 2 ) ( 1 ). When reacted with benzil, both, 1 and 2 , form the 1,2‐addition product, but in the Si/P FLP 2 , the second carbonyl function additionally binds to the silicon atom. With but‐3‐en‐2‐one 2 forms the 1,2‐addition product, while 1 binds in 1,4‐position. The reaction with acetonitrile yielded an unexpected etheneimine adduct for both systems, while only 1 reacted with tert ‐butylnitrile. With benzonitrile and acrylonitrile, 2 showed reversible addition to the C≡N bond and 1 forms a stable adduct with benzonitrile. Solely 1 shows reactivity towards phenylacetylene affording a mixture of the CH deprotonation adduct t Bu 2 P(H)−O−AlBis 2 (CCPh) and the FLP −C≡C 1,2‐addition adduct under ring formation. All compounds were characterized by multinuclear NMR spectroscopy, XRD and elemental analysis.