World Library  
Flag as Inappropriate
Email this Article


Article Id: WHEBN0005219153
Reproduction Date:

Title: Chromocene  
Author: World Heritage Encyclopedia
Language: English
Subject: Metallocenes, Ferrocene, Bis(benzene)chromium, Potassium tetraperoxochromate(V), Chromium(III) iodide
Collection: Cyclopentadienyl Complexes, Metallocenes, Organochromium Compounds
Publisher: World Heritage Encyclopedia


IUPAC name
Other names
Jmol-3D images Image
RTECS number GB7600000
Molar mass 182.19 g·mol−1
Appearance dark red crystals
Density 1.43 g/cm3
Melting point 168 to 170 °C (334 to 338 °F; 441 to 443 K)
Boiling point Sublimes (under vacuum)
see Ferrocene
0 D
Main hazards Pyrophoric
Irritant Xi
R-phrases R20/21/22-R36/37/38
S-phrases S26-S37/39-S45
NFPA 704
Related compounds
Related compounds
chromium(II) acetate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Chromocene, formally known as bis(η5-cyclopentadienyl)chromium(II), is a haptic) covalent chromium–carbon bonds.[1] Chromocene is structurally similar to ferrocene, the prototype for the metallocene class of compounds; however, as it has only 16 valence electrons, it does not follow the 18-electron rule.[2] It is a paramagnetic compound and also highly reducing, both consequences of its low valence electron count. Like structurally related metallocenes, chromocene readily sublimes in a vacuum and is soluble in non-polar organic solvents.

Ernst Otto Fischer, who shared the 1973 Nobel Prize in Chemistry for his work on sandwich compounds,[3] was the first to report a synthesis for chromocene.[4] One simple method of preparation involves the reaction of chromium(II) chloride with sodium cyclopentadienide:

CrCl2 + 2 NaC5H5 → Cr(C5H5)2 + 2 NaCl

Such syntheses are typically conducted in THF; decamethylchromocene, Cr[C5(CH3)5]2, can be prepared analogously from LiC5(CH3)5. Chromocene can also be prepared from chromium(III) chloride in a redox process:[5]

2 CrCl3 + 6 NaC5H5 → 2 Cr(C5H5)2 + C10H10 + 6 NaCl

The chromium(0) organometallic complex chromium hexacarbonyl can be oxidised by cyclopentadiene in the presence of diethylamine to produce chromocene, the removed protons being reduced to produce hydrogen gas.[6]

Cr(CO)6 + 2 C5H6 → Cr(C5H5)2 + 6 CO + H2

The structure of chromocene has been verified by X-ray crystallography; the average Cr–C bond length is 215.1(13) pm.[7]

Like some other metallocenes, the cyclopentadienyl ligands of chromocene are displaceable. When combined with catalysis.

Chromocene provides a convenient route for preparing the anhydrous form of chromium(II) acetate,[8] a useful precursor to other chromium(II) compounds. The reaction involves the displacement of cyclopentadienyl ligands by the formation of cyclopentadiene:

4 CH3COOH + 2 Cr(C5H5)2 → Cr2(O2CCH3)4 + 4 C5H6


Chromium compounds are toxic, although Cr(VI) species are usually considered more dangerous than reduced chromium compounds. Chromocene is highly reactive toward air and could ignite upon exposure to the atmosphere.


  1. ^  
  2. ^ Elschenbroich, C.; Salzer, A. (1992). Organometallics: A Concise Introduction (2nd ed.).  
  3. ^ "The Nobel Prize in Chemistry 1973".  
  4. ^  
  5. ^ Long, N. J. (1998). Metallocenes: Introduction to Sandwich Complexes. London:  
  6. ^  
  7. ^ Flower, K. R.; Hitchcock, P. B. (1996). "Crystal and molecular structure of chromocene (η5-C5H5)2Cr".  
  8. ^ Beneš, L.; Kalousová, J.; Votinský, J. (1985). "Reaction of chromocene with carboxylic acids and some derivatives of acetic acid".  
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.