1999 cyclopentane derivatives

cyclopentane derivativesQ 0030

36 - 096Catalytic Cyclization and Dimerization of 1.5-Hexadiene by Transi-tion Metals: The Reactivity of NiII and PdII Complexes ContainingBi- or Tridendate Ligands and of Bis(alkyne)nickel(0) Compounds.— Several novel Ni(II) and Pd(II) complexes containing bi- or tridentateligands [cf. (I) and (II)] are prepared and their structures studied in detailusing NMR-spectroscopy and X-ray analysis. All nickel catalysts (I) to (III)efficiently catalyze the cyclization of hexadiene (IV) in the presence of Et3Alto give a mixture of methyl- (VI) and methylenecyclopentane (V). A longinduction period is observed for this reaction probably due to formation of anovel cyclopentylaluminum cocatalyst. In the presence of methylalumoxane,hexadiene (IV) undergoes a nickel-catalyzed dimerization to furnish a mixture ofdimers, e.g. (VII) and (VIII), containing only one cyclopentane ring. Bidentateligands are more effective than tridentate ligands. The corresponding palladiumcomplexes are inactive in both cyclization and dimerization reactions. —(WALTHER, DIRK; DOEHLER, THOMAS; HEUBACH, KIRSTIN; KLOBES,OLAF; SCHWEDER, BERND; GOERLS, HELMAR; Z. Anorg. Allg. Chem.625 (1999) 6, 923-932; Inst. Anorg. Anal. Chem., Friedrich-Schiller-Univ.,D-07743 Jena, Germany; EN)

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