Niobium Bis‐ and Mono(Pentafulvene) Complexes: E−H Bond Cleavage and Insertion Reactions (E=C, N, O)

Bis(η5:η1‐(di‐para‐tolyl)pentafulvene)niobium chloride (1) reacts with methyl lithium via salt metathesis to the methylated bis(pentafulvene)niobium complex 2, and with lithium 2,6‐diisopropylanilide addition and subsequent N−H bond activation to the imido mono(pentafulvene)niobium complex 3. Avoiding the competing protonation of the chloride, bis(pentafulvene)niobium complex 2 reacts with primary aromatic and aliphatic amines to form terminal niobocene imido complexes, and with water to form the analog terminal oxo complex. Secondary methyl amines undergo a simultaneous N−H and C−H activation to form niobaaziridines under mild conditions. In contrast to other reported examples, 3 can be employed to investigate the uncontested reactivity of mono(pentafulvene)niobium complexes. Reaction with 4‐tert‐butylphenol selectively yields a niobocene phenolate complex. Unprecedented for mono(pentafulvene)niobium complexes, treating 3 with multiple‐bond‐containing substrates (nitriles, isocyanates) smoothly results the insertion into the Nb‐Cexo σ‐bond, forming the corresponding alkylidene amido and imidato complexes. Bis‐ and mono(pentafulvene)niobium complexes are prepared and the subsequent E−H bond activations and insertion reactions are performed (E=O, N, C). Thereby, terminal oxo and imido complexes, as well as phenolate, alkylideneamido, imidato and niobaaziridine complexes are received.