Expanding the Scope: Monopentafulvene and -Benzofulvene Complexes of Zirconium and Hafnium

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 pTol(2)Fv, and benzofulvenes adamantylidenebenzofulvene AdBzFv, 10,10'-di-p-tolylbenzofulvene pTol(2)BzFv, and 10,10'-diphenylbenzofulvene Ph(2)BzFv yielded the corresponding pentafulvene complexes (eta(5)-pentamethylcyclopentadieny)metal(eta(5):eta(1)-pentafulvene)-chloride (Zr2a,b, Hf2a,b) and benzofulvene complexes (eta(5)-spentamethylcyclopentadieny)metal(eta(5):eta(1)-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 pi-eta(5):sigma-eta(1) dianionic bonding mode together with slight influence of the pi-eta(2):pi-eta(3):sigma-eta(1) bonding mode. By use of the prochiral benzofulvenes the corresponding complexes Zr3a-c and Hf3a are furthermore obtained in a diastereoselective manner.