[3] The Ni center has a formal +2 charge, and the Cp rings are usually assigned as cyclopentadienyl anions (Cp−), related to cyclopentadiene by deprotonation.

The two remaining d-electrons each reside in the dyz and dxz orbitals, giving rise to the molecule's paramagnetism, as manifested in the unusually high field chemical shift observed in its 1H NMR spectrum.

[4] It has been prepared in a one-pot reaction, by deprotonating cyclopentadiene with ethylmagnesium bromide, and adding anhydrous nickel(II) acetylacetonate.

[5] A modern synthesis entails treatment of anhydrous sources of NiCl2 (such as hexaamminenickel chloride) with sodium cyclopentadienyl:[6] Like many organometallic compounds, Ni(C5H5)2 does not tolerate extended exposure to air before noticeable decomposition.

Nickelocene reacts with nitric acid to produce cyclopentadienyl nickel nitrosyl, a highly toxic organonickel compound.