Editing Ferrocene (section)

===Via alkali cyclopentadienide===
More efficient preparative methods are generally a modification of the original [[transmetalation]] sequence using either commercially available [[sodium cyclopentadienide]]<ref name = orgsyn /> or freshly [[dicyclopentadiene|cracked]] cyclopentadiene deprotonated with [[potassium hydroxide]]<ref>{{cite book| vauthors = Jolly WL |title= The Synthesis and Characterization of Inorganic Compounds |url=https://archive.org/details/synthesischaract0000joll|url-access=registration|publisher=Prentice-Hall |location=New Jersey |date=1970|isbn= 9780138799328}}</ref> and reacted with anhydrous iron(II) chloride in ethereal solvents.

Modern modifications of Pauson and Kealy's original Grignard approach are known:

*Using sodium cyclopentadienide: &nbsp; &nbsp; &nbsp; 2&nbsp;NaC<sub>5</sub>H<sub>5</sub> &nbsp; + &nbsp; FeCl<sub>2</sub> &nbsp; → &nbsp; Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> &nbsp; + &nbsp; 2&nbsp;NaCl
*Using freshly-cracked cyclopentadiene: &nbsp; &nbsp; FeCl<sub>2</sub>·4H<sub>2</sub>O &nbsp; + &nbsp; 2&nbsp;C<sub>5</sub>H<sub>6</sub> &nbsp; + &nbsp; 2&nbsp;KOH &nbsp; → &nbsp; Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> &nbsp; + &nbsp; 2&nbsp;KCl &nbsp; + &nbsp; 6&nbsp;H<sub>2</sub>O
*Using an iron(II) salt with a Grignard reagent: &nbsp; &nbsp; 2&nbsp;C<sub>5</sub>H<sub>5</sub>MgBr &nbsp; + &nbsp; FeCl<sub>2</sub> &nbsp; → &nbsp; Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> &nbsp; + &nbsp; 2&nbsp;MgBrCl

Even some [[amine]] bases (such as [[diethylamine]]) can be used for the deprotonation, though the reaction proceeds more slowly than when using stronger bases:<ref name=orgsyn>{{OrgSynth|title = Ferrocene|authorlink = Geoffrey Wilkinson| vauthors = Wilkinson G |volume = 36|page = 31|year = 1956|doi = 10.15227/orgsyn.036.0031}}</ref>

:2&nbsp;C<sub>5</sub>H<sub>6</sub> &nbsp; + &nbsp; 2&nbsp;(CH<sub>3</sub>CH<sub>2</sub>)<sub>2</sub>NH &nbsp; + &nbsp; FeCl<sub>2</sub> &nbsp; → &nbsp; Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> &nbsp; + &nbsp; 2&nbsp;(CH<sub>3</sub>CH<sub>2</sub>)<sub>2</sub>NH<sub>2</sub>Cl

Direct transmetalation can also be used to prepare ferrocene from some other metallocenes, such as [[manganocene]]:<ref>{{cite journal | vauthors = Wilkinson G, Cotton FA, Birmingham JM |author-link1= Geoffrey Wilkinson |year= 1956|title= On manganese cyclopentadienide and some chemical reactions of neutral bis-cyclopentadienyl metal compounds|journal= [[J. Inorg. Nucl. Chem.]]|volume= 2|issue= 2|pages= 95–113|doi=10.1016/0022-1902(56)80004-3}}</ref>
:FeCl<sub>2</sub> &nbsp; + &nbsp; Mn(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> &nbsp; → &nbsp; MnCl<sub>2</sub> &nbsp; + &nbsp; Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>