[2] After the development of valence bond theory in 1928, benzene was described primarily using its two major resonance contributors, the two Kekulé structures.

[16] Attempting a similar reaction with potassium tetrachloroplatinate results in the formation of a pentamethylcyclopentadiene complex, [(η4-Cp*H)PtCl2], indicating that the rhodium and iridium metal centres are necessary for the step in which the aromatic anion is formed.

By varying the amount of DMDO, either the mono- or diepoxide can be formed, with the oxygen atoms exo on the bicyclic carbon framework.

[21] NMR had previously hinted at a pentagonal pyramidal structure in a related cation[22] as had spectral data on the Hogeveen and Kwant dication.

[25] From the perspective of organometallic chemistry, the species can be viewed as having a carbon(IV) centre (C4+) bound to an aromatic η5–pentamethylcyclopentadienyl anion (six-electron donor) and a methyl anion (two-electron donor), thereby satisfying the octet rule[26] and being analogous to the gas-phase organozinc monomer [(η5–C5(CH3)5)Zn(CH3)], which has the same ligands bound to a zinc(II) centre (Zn2+) and satisfies the 18 electron rule on the metal.