A niobium pentafulvene ethylene complex: synthesis, properties and reaction pathways.

The π-η:σ-η coordination mode of early transition metal pentafulvene ligands yields a strongly nucleophilic exocyclic carbon atom (C). The substitution of the chlorido ligand of bis(η:η-(di--tolyl)pentafulvene)niobium chloride (1) by reaction with ethyl magnesium bromide is subsequently followed by a β-C-H activation employing this C, forming the pentafulvene niobium ethylene complex 2. The intermediately formed ethyl complex can be intercepted with water, protonating both pentafulvene moieties and thereby retaining the ethyl moiety to give the terminal oxo complex 3.