Chromocene 5219153 206518067 2008-04-18T16:32:53Z Benjah-bmm27 126395 [[skeletal formula]] added {{Chembox new | Name = Chromocene | ImageFileL1 = Chromocene-2D-skeletal.png | ImageSizeL1 = 100px | ImageNameL1 = Chromocene | ImageFileR1 = Chromocene-3D-balls.png | ImageSizeR1 = 150px | ImageNameR1 = Chromocene | IUPACName = chromocene | OtherNames = Chromocene,<br />Bis(cyclopentadienyl)-<br />chromium(II) | Section1 = {{Chembox Identifiers | SMILES = | CASNo = 1271-24-5 | RTECS = GB7600000 }} | Section2 = {{Chembox Properties | Formula = C<sub>10</sub>H<sub>10</sub>Cr | MolarMass = 182.18 g/mol | Appearance = dark red crystals | Density = 1.43 g/cm<sup>3</sup>, solid | Solubility = decomposes in water | MeltingPt = 168-170 °C | BoilingPt = sublimes (under vacuum) }} | Section3 = {{Chembox Structure | Coordination = pseudooctahedral<br /> see [[Ferrocene]] | CrystalStruct = | Dipole = 0 [[Debye|D]] }} | Section7 = {{Chembox Hazards | ExternalMSDS = | MainHazards = pyrophoric | FlashPt = | RPhrases = 20/21/22-36/37/38 | SPhrases = 26-37/39 }} | Section8 = {{Chembox Related | OtherCpds = [[Ferrocene|Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>]]<br />[[Nickelocene|Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>]]<br /> [[Chromium(II) acetate]] }} }} '''Chromocene''' is an [[Organometallic chemistry|organometallic]] compound with the formula Cr(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>. It is also often abbreviated Cp<sub>2</sub>Cr. This sandwich compound is structurally similar to [[ferrocene]] but paramagnetic and far more reactive. Also like structurally related [[metallocene]]s, chromocene sublimes readily in a vacuum and is soluble in non-polar organic solvents. It is prepared by the following route: :[[Chromium(II) chloride|CrCl<sub>2</sub>]] + 2 Na[[Cyclopentadienyl complex|C<sub>5</sub>H<sub>5</sub>]] → Cr(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> + 2 NaCl Such syntheses are typically conducted in [[THF]] solution. The strongly reducing analogue decamethylchromocene, Cr[C<sub>5</sub>(CH<sub>3</sub>)<sub>5</sub>]<sub>2</sub>, is prepared analogously from [[Pentamethylcyclopentadiene|LiC<sub>5</sub>(CH<sub>3</sub>)<sub>5</sub>]]. Like some other metallocenes, the C<sub>5</sub>H<sub>5</sub> ligands are displaceable. Thus, chromocene in combination with [[silica gel]] gives the Phillips 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. A large percentage of the industrial production of polyethylene is attributable to such chromium-based catalysts. ==Safety== Chromium compounds are toxic, although [[Chromate|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== {{Unreferenced|date =September 2007}} <references/> [[Category:Chromium compounds]] [[Category:Metallocenes]] [[ar:كروموسين]] [[ca:Plantilla:Chembox]] [[es:Plantilla:Chembox]] [[fr:Modèle:Chimiebox général]]