Carbene oligomerization promoted by nickelocene derived complexes

• New cyclopentadienylnickel systems for carbene oligomerization were developed.
• Cyclopentadienylnickel-NHC complex/MAO catalyst gave polymer of Mw = 21,800 Da.
• A coordination–insertion mechanism for carbene oligomerization is proposed.

New catalytic systems based on nickelocene were used as initiators in polymerization of ethyl acetate carbene derived from ethyl diazoacetate. Nickelocene itself and nickelocene activated with n-butyllithium or diphenylmethyllithium led to the formation of oligomers with average molecular weight about 800 Da. η5-Cyclopentadienyl(1,3-diallyl-imidazolin-2-ylidene)nickel bromide activated with an excess of methylalumoxane gave ethyl acetate carbene polymer with average molecular weight 21,800 Da. MALDI TOF spectra indicate coordination–insertion mechanism of polymerization in all catalytic systems applied.

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