Editing Metallocene (section)

===Using cyclopentadienyl reagents===
A variety of reagents have been developed that transfer Cp to metals. Once popular was [[thallium cyclopentadienide]]. It reacts with metal halides to give thallium chloride, which is poorly soluble, and the [[cyclopentadienyl complex]]. Trialkyl[[tin]] derivatives of Cp<sup>−</sup> have also been used.

Many other methods have been developed. [[Chromocene]] can be prepared from [[chromium hexacarbonyl]] by direct reaction with cyclopentadiene in the presence of [[diethylamine]]; in this case, the formal deprotonation of the cyclopentadiene is followed by [[redox|reduction]] of the resulting protons to [[hydrogen]] gas, facilitating the [[oxidation]] of the metal centre.<ref>{{cite journal|last1= Fischer|first1= E. O.|author-link1= Ernst Otto Fischer|last2= Hafner|first2= W.|year= 1955|title= Cyclopentadienyl-Chrom-Tricarbonyl-Wasserstoff|trans-title=Cyclopentadienylchromium tricarbonyl hydride|journal= [[Z. Naturforsch. B]]|volume= 10|issue= 3|pages= 140–143|language= de|doi=10.1515/znb-1955-0303|s2cid= 209650632|doi-access= free}}</ref>

:Cr(CO)<sub>6</sub> + 2&nbsp;C<sub>5</sub>H<sub>6</sub> → Cr(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> + 6&nbsp;CO + H<sub>2</sub>

Metallocenes generally have high thermal stability. Ferrocene can be sublimed in air at over 100&nbsp;°C with no decomposition; metallocenes are generally purified in the laboratory by vacuum [[sublimation (chemistry)|sublimation]]. Industrially, sublimation is not practical so metallocenes are isolated by crystallization or produced as part of a hydrocarbon solution. For Group IV metallocenes, donor solvents like ether or THF are distinctly undesirable for polyolefin catalysis.  Charge-neutral metallocenes are soluble in common organic solvents. Alkyl substitution on the metallocene increases the solubility in hydrocarbon solvents.