Preparation and structural features of 1-(2-pyridyl)- and 1-(2-furyl)indenyl-zirconium complexes

Addition of 2-lithiopyridine to 1-indanone followed by aqueous workup gave 1-(2-pyridyl)indanol (3); subsequent H+-catalyzed H2O-elimination gave 3-(2-pyridyl)indene 4. Deprotonation with n-butyllithium yielded the corresponding anionic reagent 5. Treatment of 4 with Zr(NR2)4 (R=CH3 or C2H5) yielded the half-sandwich complexes η5-[1-(2-pyridyl)indenyl]Zr(NR2)3 (7a, 7b). Reaction of 5 with CpZrCl3 led to the formation of η5-[1-(2-pyridyl)indenyl]CpZrCl2 (8). The compounds 3, 4, and 8 were characterized by X-ray diffraction. Analogous treatment of 1-indanone with 2-lithio-5-methylfuran, followed by H2O-elimination and deprotonation gave the reagent [1-(5-methyl-2-furyl)indenyl]Li·(OEt2) 13. Its reaction with ZrCl4 in a 2:1 ratio in toluene yielded a 60:40 mixture of rac- and meso-bis[η5-1-(5-methyl-2-furyl)indenyl]ZrCl2 (rac-14 and meso-14). Crystallization gave pure rac-14, which was characterized by an X-ray crystal structure analysis. Treatment of rac-14 with excess methylalumoxane (MAO) in toluene (Al:Zr≈2000) gave an active homogeneous Ziegler catalyst for atactic propene polymerization, whereas the 8–MAO system was inactive.