Frustrated Lewis Pair‐Type Reactivity of Intermolecular Rare‐Earth Aryloxide and N‐Heterocyclic Carbene/Olefin Combinations

Abstract

This work reports the cooperative reactivity of rare‐earth aryloxide complexes with N‐heterocyclic carbene (NHC) or N‐heterocyclic olefin (NHO), showcasing their synergistic effect in the activation of H2 and diverse organic substrates. Reactions of RE(OAr)3 (RE = La, Sm, and Y; Ar = 2,6‐tBu2‐C6H3) with unsaturated NHC ItBu (:C[N(R)CH]2, R = tBu) isolate abnormally bound RE metal NHC complexes RE/aNHC. In contrast, no metal‐NHO adducts were formed when RE(OAr)3 were treated with NHO (R2C=C[N(R)C(R)]2, R = CH3). Both RE/aNHC and RE/NHO Lewis pairs enabled cooperative H2 activation. Furthermore, RE(OAr)3 were found to catalyze the hydrogenation of exocyclic C=C double bond of NHO under mild conditions. Moreover, treatment of the La/aNHC complex with benzaldehyde produced a La/C4 1,2‐addition product. The La/NHO Lewis pair could react with (trimethylsilyl)diazomethane and a, b‐conjugated imine, affording an isocyanotrimethylsilyl lanthanum amide complex and a La/C 1,4‐addition product, respectively.