| Chromocene | |
|---|---|
 |
 |
| IUPAC name |
chromocene, bis(η5-cyclopentadienyl)chromium
|
| Other names | CrCp2 |
| Identifiers | |
| CAS number | 1271-24-5 |
| ChEBI | 30677 |
| RTECS number | GB7600000 |
| Properties | |
| Molecular formula | C10H10Cr |
| Molar mass | 182.18 g/mol |
| Appearance | dark red crystals |
| Density | 1.43 g/cm3, solid |
| Melting point |
168-170 °C |
| Boiling point |
sublimes (under vacuum) |
| Solubility in water | decomposes in water |
| Structure | |
| Coordination geometry |
pseudooctahedral see Ferrocene |
| Dipole moment | 0 D |
| Hazards | |
| R-phrases | 20/21/22-36/37/38 |
| S-phrases | 26-37/39 |
| Related compounds | |
| Related compounds | Fe(C5H5)2 Ni(C5H5)2 Chromium(II) acetate |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
| Infobox references | |
Chromocene is an organometallic compound with the formula Cr(C5H5)2. It is also often abbreviated Cp2Cr. This sandwich compound is structurally similar to ferrocene but does not follow the 18-electron rule because it only has 16 electrons and therefore it also paramagnetic and far more reactive. Also like structurally related metallocenes, chromocene sublimes readily in a vacuum and is soluble in non-polar organic solvents.
It is prepared by the following route:
Such syntheses are typically conducted in THF solution. The strongly reducing analogue decamethylchromocene, Cr[C5(CH3)5]2, is prepared analogously from LiC5(CH3)5.
Like some other metallocenes, the C5H5 ligands are displaceable. Thus, chromocene in combination with silica gel gives the Union Carbide catalyst for the polymerization of ethylene, although other preparations exist for this important catalyst. The chromocene decomposes on the silica surface to generate high reactive organometallic centers that are responsible for the catalysis.
Safety
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 inflame upon exposure to the atmosphere.
General reading
- C. Elschenbroich, A. Salzer ”Organometallics : A Concise Introduction” (2nd Ed) (1992) from Wiley-VCH: Weinheim. ISBN 3-527-28165-7
References
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