ChemInform Abstract: Arene Derivatives of Zirconium(II) and Hafnium(II).

ChemInform Abstract

In a search for Zr and Hf organometallics in oxidation states lower than four, the title compounds are tried to prepare as olefin polymerization precursors. The reaction of ZrCl₄ with Al/AlCl3/aromatic hydrocarbon (toluene, 1,3,5-trimethylbenzene) systems leads to solutions containing Zr(II)-arene complexes. For the cases shown in the scheme the solid compounds (IV) are obtained. The complex (IVb) can also be obtained by ligand-exchange reaction from (IVa) with (IIb) or by ligand-synthesis reaction from (IVa) and but-2-yne. Spectroscopic evidence for the existence in solution of the corresponding Hf(II)-η6-arene complexes is given. Treatment of (IVb) with water gives (V). An analogous trinuclear species as dication and isolated as its Al₂Cl₇ salt is obtained in 70% yield by reducing ZrCl₄ with stoichiometric amount of Al and AlCl₃ in the presence of hexamethylbenzene.