Reactivity of Lutetacyclopropene toward Benzyl, Benzoyl, and Trimethylsilyl Nitriles Affording Diversified Lutetium Complexes

Although the reaction of metallacyclopropenes toward alkyl and aryl nitriles has been extensively studied, their reactivity toward other types of nitriles, e.g., benzyl and benzoyl nitriles, that often behave multifunctionally was rarely explored. Herein, we demonstrated the unique reactivity of lutetacyclopropene 1 with benzyl, benzoyl, and trimethylsilyl nitriles. Treatment of 1 with 2 equiv of ArCH2CN (Ar = Ph or 2,6-Me2C6H3) led to acyclic lutetium complexes 2 with both keteniminate and vinyl-enamide ligands. Isolation of lutetacyclic enamine intermediate 4 indicates that the formation of 2 proceeds through three key steps: the initial insertion of CN bond into Lu–Csp2 bond giving azalutetacyclopentadiene intermediates 3, tautomerization of 3 via 1,3-H shift providing 4, and subsequent intermolecular proton transfer between 4 and ArCH2CN. However, when 1 was allowed to react with benzoyl or trimethylsilyl nitrile, bis-isocyanide complex 5 was obtained with the release of 1,2-dibenzoyl-1,2-diphenylethene or 1,2-di­(trimethylsilyl)-1,2-diphenylethene, respectively. The formation of 2 and 5 represents two previously unreported reaction modes between metallacyclopropenes and nitriles.