Intramolecular coordination of an alkene to a mixed dicyclopentadienyl benzyl zirconium cation studied by NMR spectroscopy

Benzylation of [Zr(¿5-C5H5){¿5-C5H4SiMe2(CH2CH:CH2)}Cl2] 1 yields [Zr(¿5-C5H5){¿5-C5H4SiMe2(CH2CH:CH2)}(CH2Ph)2] 2, which reacts with either B(C6F5)3 or [Ph3C][B(C6F5)4] to generate the same 14-electron cationic species, [Zr(¿5-C5H5){¿5-C5H4SiMe2(CH2CH:CH2)}(CH2Ph)]+ 3, which was fully characterized by 1H, 13C NMR and 1H DNMR spectroscopy. 3 Was fluxional in soln. Stabilization of 3 occurs by interaction of the ¿-bonding alkene orbital with the vacant 2a1 zirconium orbital and simultaneous overlapping of the HOMO ¿ alkene orbital with the vacant zirconium orbital of the same symmetry, b2. These interactions result in delocalized electron d. in the Zr-C-C system.Financial support of our work by DGICTY (Project PB- 92/0178-C) and CAM(I+D0034/94) is gratefully acknowledged. G. H. is grateful to the University of Alcala for financial support and the Alexander von Humboldt-Stiftung for a fellowshi