Expanding the Scope: Monopentafulvene and -Benzofulvene Complexes of Zirconium and Hafnium
Fischer M., Oswald T., Ebert H., Schmidtmann M., Beckhaus R.
The reaction of Cp∗MCl3 (M = Zr, Zr1; M = Hf, Hf1) with the reducing agent Na/Hg (20% Na) and with sterically encumbered pentafulvenes adamantylidenepentafulvene AdFv, 6,6′-di-p-tolylpentafulvene pTol2Fv, and benzofulvenes adamantylidenebenzofulvene AdBzFv, 10,10′-di-p-tolylbenzofulvene pTol2BzFv, and 10,10′-diphenylbenzofulvene Ph2BzFv yielded the corresponding pentafulvene complexes (η5-pentamethylcyclopentadienyl)metal(η5:η1-pentafulvene)chloride (Zr2a,b, Hf2a,b) and benzofulvene complexes (η5-pentamethylcyclopentadienyl)metal(η5:η1-benzofulvene)chloride (Zr3a-c, Hf3a). This reductive complexation approach can be used in a multigram scale and mostly very good yields (up to 92%). In addition to NMR spectroscopic analyses, the pentafulvene complex Zr2b and benzofulvene complex Zr3b were characterized by X-ray crystallography, showing mainly the π-η5:σ-η1 dianionic bonding mode together with slight influence of the π-η2:π-η3:σ-η1 bonding mode. By use of the prochiral benzofulvenes the corresponding complexes Zr3a-c and Hf3a are furthermore obtained in a diastereoselective manner.