Zirconocene complexes bearing novel 3-dimethylamino-1,2-dihydropentalene derived ligand systems

Abstract

Coupling of the N,N-dimethylacrylamides 6a–c with cyclopentadienide resulted in the formation of the substituted 3-dimethylamino-1,2-dihydropentalnenes 2a–c. Deprotonation followed by metallation with CpZrCl₃·DME gave the substituted zirconocenes 12a–c. The reaction of 3-dimethylamino-1-methyl-dihydropentalene 2a with ZrCl₂(NMe₂)₂·2THF resulted in a unique coupling between a pair of the aminodihydropentalene derivatives to yield an unsymmetrically bridged novel ansa-zirconocene framework (9a). Treatment of the 1,1-dimethyl-substituted substrate 2b with this Zr-amido reagent in contrast resulted in a clean deprotonation and formation of the unbridged bis(dimethylaminohydropentalenyl)ZrCl₂ complexes 10b. The compounds 2a, 9a, meso-10b, 12a and 12c were characterized by X-ray diffraction.