Metallocenes are the family of MCp2 (where M - metal ion and Cp - cyclopentadienyl ring,) compounds that have been serendipitously discovered about 70 years ago and ignited a new branch of chemistry: organometallics. Although its first-synthesized, most stable and most well-known representative, ferrocene, has been thoroughly investigated over decades, its phase diagram and pressure behaviour have been only recently explored. Nickelocene is one of the isostructural analogues of ferrocene. Although, resembling ferrocene molecular and crystal structure, it does not comply with 18-electron rule, which in consequences gives huge instability of the system, structurally manifested in a significant elongation of metal–cyclopentadienyl ring organometallic bonds. We would like to explore pressure-driven transformations and reactivity of nickelocene. Due to the relatively large instability of nickelocene, we also expect its higher reactivity under pressure when exposed to high pressure.