metallocenes

https://doi.org/10.1351/goldbook.M03865
Organometallic @C01329@ compounds in which one atom of a transition metal such as iron, ruthenium or osmium is bonded to and only to the face of two cyclopentadienyl [η5-(C5H5)] @L03518@ which lie in parallel planes. The term should not be used for analogues having rings other than cyclopentadienyl as @L03518@.
M03865.png
Source:
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1349 [Terms] [Paper]