Question

Cp2Ni undergoes oxidative addition of PhI. How does this reaction happen? Be sure to clearly sketch the product and describe the steps between the reactants and products.

Answer 1

I am sure that the product would be the one I have sketched. The mechanistic details are subject to debate and cannot be told for certain without literature precedent. However, this is what I feel should be correct.

Nickelocene is a 20 electron complex Ni (II): 8 electrons 2 Cp rings: 2*6 electrons The majority of chemistry of nickelocene is thus dominated by its tendency to undergo oxidation to form the significantly more 18 electron complex usually by the loss of or the change of hapticity to the cyclopentadienyl rings A reaction with Phl would thus probably involve a loss of a cyclopentadienyl ring to form an unstable 14 e intermediate. The Ni (II) would insert into the C-H bond of iodobenzene. The coordination sphere would be completed by the I ion. . Ср Phl Ср Ni Ni 16 e complex, Ni as Ni(lV) Ni as Ni(ll) Oxidative addition Ni(II) to Ni(IV) The most likely route is that the hydrogen is abstracted by the cyclopentaduenyl ring to yield cyclopentane