HIGHLY SELECTIVE MONOFUNCTIONALIZATION OF ZIRCONACYCLOPENTANES AND DIALKYLZIRCONOCENE COMPLEXES

Selective monofunctionalization was investigated for symmetrical zirco nacyclopentanes or symmetrical dialkylzirconocenes. Reaction of zircon acyclopentanes, which were prepared by intermolecular coupling of two alkenes, or intramolecular cyclization of dienes, trienes or tetraenes on zirconium, with PPh(2)Cl or SnR(3)Cl (R = Me, Ph) gave monofunctio nalized products in good to high yields with high selectivities. Even in the presence of 2 equiv, of PPh(2)Cl or SnR(3)Cl, only one Zr-carbo n bond reacted. Treatment of zirconacycropentanes with methanol yielde d monoprotonated complexes. Subsequent addition of halogen such as Br- 2 and I-2 to these monoprotonated complexes gave highly selective mono halogenated products. Similar monoprotonation reactions proceeded for dialkylzirconocene or -hafnocene complexes. Reaction of Cp(2)MR(2) (M = Zr or Hf, R = alkyl or aryl) with alcohols afforded alkylalkoxyzirco nocene or -hafnocene complexes, Cp(2)MR(OR') (M = Zr or Hf, R' = alkyl or aryl) in high yields with high selectivities. High selectivity of monofunctionalization using PPh(2)Cl, SnR(3)Cl or alcohols can be attr ibuted to the different reactivities between monoalkylzirconocenes whi ch are monofunctionalized products and zirconacyclopentanes or dialkyl zirconocenes.