An insertion and Cycloaddition reaction of Dimethylketene with di-π-cyclopentadienylnickel

The complex (π-cyclopentadienyl)σ-α,α-dimethyl-α-{2-3-π-7,7-dimethyl-6-oxobicyclo3.2.0]hept-2-en-4-yl]}acetyl]nickel (II) has been identified as the principal product of the reaction of two moles of dimethylketene with di-π-cyclopentadienylnickel. Degradation of II in methanol solution yielded methyl α,α,7,7-tetramethyl-6-oxobicyclo3.2.0]hept-2-ene-4-acetate (III); and reduction of II gave the 6-hydroxy nickel complex (VI). Complex II is a result of 1,2-cycloaddition of one ketene function to a cyclopentadienyl ring and insertion of a second ketene function into a nickelcarbon bond.