[2] It was first synthesized by Ernst Otto Fischer and Heinrich Grumbert via the reaction of osmium(IV) chloride with excess sodium cyclopentadienide in dimethoxyethane, where osmium(II) chloride is presumed to be an intermediate formed in situ.

Alternatively, cyclopentadienyl magnesium bromide could be reacted with osmium(IV) chloride, though this has worse yields.

[2] Compared to ferrocene and ruthenocene, osmocene is less reactive towards electrophilic aromatic substitution but has the greatest tendency towards adduct formation with Lewis acids.

[4] The osmocenium cation [Os(C5H5)2]+ dimerizes, forming a binuclear complex with an Os-Os bond.

[6] In 2009, Horst Kunkely and Arnd Vogler reported the possibility of photocatalytic water splitting with osmocene as a catalyst.