DIALLYLDICYCLOPENTADIENYLZIRCONIUM AND SOME RELATED COMPLEXES

The complexes Cp2Zr(C3H5)2, Cp2ZrCl(C3H5) (impure) and Cp4Zr2Cl(C3H5)3 were prepared in crystalline form by reaction of Cp2ZrCl2 with allylmagnesium chloride in THF. In a similar way, the 2-methylallyl complexes Cp2Zr(C4H7)2 and Cp2ZrCl(C4H7) were obtained as oils. The complexes are air sensitive. Infrared spectroscopy shows that the allylic ligands in Cp2ZrCl(C3H5) and Cp2ZrCl(C4H7) are σ-bonded to the metal, while in Cp2Zr(C3H5)2 and Cp2Zr(C4H7)2 one of the allylic ligands is π-bonded, the other σ-bonded. In Cp4Zr2Cl(C3H5)3, which is probably a molecular complex, one allyl group is π-bonded, the other two σ-bonded. The NMR spectra of the allylic ligands are of the dynamic type. The bonding of the allylic ligands are their CC stretching frequencies are discussed and compared with corresponding titanium and vanadium complexes; it is found that substitution of the hydrogen atom at 2-C of the allyl group by a methyl group leads to an increase of the CC stretching frequency of σ-allylic ligands, but to a decrease in the case of π-allylic ligands. © 1968.