Collect. Czech. Chem. Commun. 1997, 62, 318-324

Stereochemical Factors of γ-H Eliminationin Cyclopentadienylvinylnickel Compounds

Antoni Pietrzykowski, Stanisław Pasynkiewicz and Piotr Buchalski

Warsaw University of Technology, Faculty of Chemistry, Koszykowa 75, 00-662 Warsaw, Poland


The reactions of nickelocene with cis-1,2-diphenylpropylmagnesium bromide and with trans-1,2-diphenylpropenyllithium had been studied. It was found that cis-1,2-diphenylpropenylcyclopentadienylnickel underwent γ-H elimination to form a mixture of (η5-cyclopentadienyl)[η3-1,2-(anti)-diphenylpropenyl]nickel and (η5-cyclopentadienyl)[η3-1,2-(syn)-diphenylpropenyl]nickel as the main products. The mechanism of this reaction has been discussed. Dihydrotetra(cyclopentadienylnickel) cluster (NiCp)4H2 was the main organometallic product of the reaction of nickelocene with trans-1,2-diphenylpropenyllithium. There was no γ-H elimination products formed in this reaction. It has been concluded that γ-H elimination in cyclopentadienylvinylnickel compounds is stereochemically controlled process and can occur only if a distance of γ-hydrogen from the nickel atom is relatively small.

Keywords: Hydrogen elimination; π-Allyl complexes; Nickel.