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

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 on the activation of H 2 and diverse organic substrates. Reactions of RE(OAr) 3 (RE=La, Sm, and Y; Ar=2,6- t Bu 2 -C 6 H 3 ) with unsaturated NHC I t Bu (:C[N(R)CH] 2 , R= t Bu) isolated abnormally bound RE metal NHC complexes RE/aNHC. In contrast, no metal-NHO adducts were formed when RE(OAr) 3 were treated with NHO (R 2 C=C[N(R)C(R)] 2 , R=CH 3 ). Both RE/aNHC and RE/NHO Lewis pairs enabled cooperative H 2 activation. Furthermore, RE(OAr) 3 were found to catalyze the hydrogenation of the 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 α, β-conjugated imine, affording an isocyanotrimethylsilyl lanthanum amide complex and a La/C 1,4-addition product, respectively.