Sodium cyclopentadienide

<h2 id="preparation">Preparation</h2>
The first salt of cyclopentadienide to be reported was potassium cyclopentadienide, prepared by <a href="/facts/Johannes_Thiele_(chemist)/5upR3Kvg">Johannes Thiele</a>. In 1901 there was not much interest in the topic.<a class="footnote-ref" id="fnref:3" href="#fn:3">3</a>
Sodium cyclopentadienyl is prepared by treating <a href="/facts/Cyclopentadiene/S66eVYvh">cyclopentadiene</a> with <a href="/facts/Sodium/eYuSPu2V">sodium</a>:<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a>

2 Na + 2 C5H6 → 2 NaC5H5 + H2
The conversion can be conducted by heating a suspension of molten sodium in <a href="/facts/Dicyclopentadiene/vck23a49">dicyclopentadiene</a>.<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a> In former times, the sodium was provided in the form of "sodium wire" or "sodium sand", a fine dispersion of sodium prepared by melting sodium in refluxing <a href="/facts/Xylene/BEGggD9s">xylene</a> and rapidly stirring.<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a><a class="footnote-ref" id="fnref:7" href="#fn:7">7</a> <a href="/facts/Sodium_hydride/Pnsh2T64">Sodium hydride</a> is a convenient base:<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a>

NaH + C5H6 → NaC5H5 + H2
In early work, <a href="/facts/Grignard_reagent/0vkLtPo1">Grignard reagents</a> were used as bases. With a <a href="/facts/Acid_dissociation_constant/t4YyRtKC">pKa</a> of 15, cyclopentadiene can be deprotonated by many reagents.
Sodium cyclopentadienide is commercially available as a solution in <a href="/facts/Tetrahydrofuran/P5t6SkMK">THF</a>.

<h2 id="applications">Applications</h2>
Sodium cyclopentadienide is a common reagent for the preparation of <a href="/facts/Metallocene/AecA5Qrk">metallocenes</a>. For example, the preparation of <a href="/facts/Ferrocene/jKtu9Cp8">ferrocene</a><a class="footnote-ref" id="fnref:9" href="#fn:9">9</a> and <a href="/facts/Zirconocene_dichloride/q7ggJln2">zirconocene dichloride</a>:<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a>

2 NaC5H5 + FeCl2 → Fe(C5H5)2 + 2 NaCl
ZrCl4(thf)2 + 2 NaCp → (C5H5)2ZrCl2 + 2 NaCl + 2 THF
Sodium cyclopentadienide is also used for the preparation of substituted cyclopentadienyl derivatives such as the ester and formyl derivatives:<a class="footnote-ref" id="fnref:11" href="#fn:11">11</a>

NaC5H5 + O=C(OEt)2 → NaC5H4CO2Et + NaOEt
These compounds are used to prepare substituted metallocenes such as <a href="/facts/1%2c1%2527-Ferrocenedicarboxylic_acid/2Dt8vWWv">1,1'-ferrocenedicarboxylic acid</a>.<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a>

<h2 id="structure">Structure</h2>
The nature of NaCp depends strongly on its medium and for the purposes of planning syntheses; the reagent is often represented as a salt Na+C5H−5. Crystalline solvent-free NaCp, which is rarely encountered, is a "polydecker" <a href="/facts/Sandwich_complex/uhupMGDU">sandwich complex</a>, consisting of an infinite chain of alternating Na+ centers sandwiched between <a href="/facts/Bridging_ligand/E4ytba8I">μ</a>-<a href="/facts/Hapticity/7MDtzehL">η5</a>:η5-C5H5 ligands.<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a> As a solution in donor solvents, NaCp is highly solvated, especially at the alkali metal as suggested by the isolability of the <a href="/facts/Adduct/vBpTmotm">adduct</a> Na(<a href="/facts/Tmeda/fC8RDdxs">tmeda</a>)Cp.<a class="footnote-ref" id="fnref:14" href="#fn:14">14</a>
In contrast to alkali metal cyclopentadienides, <a href="/facts/Tetrabutylammonium/thxACdb6">tetrabutylammonium</a> cyclopentadienide (Bu4N+C5H−5) was found to be supported entirely by ionic bonding and its structure is representative of the structure of the cyclopentadienide anion (C5H−5, Cp−) in the solid state. However, the anion deviates somewhat from a planar, regular pentagon, with C–C bond lengths ranging from 138.0 -140.1 pm and C–C–C bond angles ranging from 107.5-108.8°.<a class="footnote-ref" id="fnref:15" href="#fn:15">15</a>

<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Lithium_cyclopentadienide/Iyy0b5b8">Lithium cyclopentadienide</a></li>
<li>Potassium cyclopentadienyl</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1">International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSC–IUPAC. ISBN 0-85404-438-8. p. 262. Electronic version. <a href="/wiki/International_Union_of_Pure_and_Applied_Chemistry" target="_blank">/wiki/International_Union_of_Pure_and_Applied_Chemistry</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">Tarun K. Panda, Michael T. Gamer, Peter W. Roesky "An Improved Synthesis of Sodium and Potassium Cyclopentadienide" Organometallics, 2003, 22, 877–878.doi:10.1021/om0207865 <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">Johannes Thiele (January 1901). "Ueber Abkömmlinge des Cyclopentadiëns". Berichte der Deutschen Chemischen Gesellschaft (in German). 34 (1): 68–71. doi:10.1002/CBER.19010340114. ISSN 0365-9496. Wikidata Q126217369. <a href="/wiki/Johannes_Thiele_(chemist)" target="_blank">/wiki/Johannes_Thiele_(chemist)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Cotton, F. Albert; Wilkinson, Geoffrey (1988), Advanced Inorganic Chemistry (5th ed.), New York: Wiley-Interscience, p. 139, ISBN 0-471-84997-9 <a href="0-471-84997-9" target="_blank">0-471-84997-9</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">Tarun K. Panda, Michael T. Gamer, Peter W. Roesky "An Improved Synthesis of Sodium and Potassium Cyclopentadienide" Organometallics, 2003, 22, 877–878.doi:10.1021/om0207865 <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">Wilkinson, Geoffrey (1963). "Ferrocene". Organic Syntheses; Collected Volumes, vol. 4, p. 473. <a href="/wiki/Geoffrey_Wilkinson" target="_blank">/wiki/Geoffrey_Wilkinson</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">Partridge, John J.; Chadha, Naresh K.; Uskokovic, Milan R. (1990). "An asymmetric hydroboration of 5-substituted cyclopentadienes: synthesis of methyl (1R,5R)-5-hydroxy-2-cyclopentene-1-acetate". Organic Syntheses{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 7, p. 339. <a href="http://www.orgsyn.org/demo.aspx?prep=cv7p0339" target="_blank">http://www.orgsyn.org/demo.aspx?prep=cv7p0339</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">Girolami, G. S.; Rauchfuss, T. B. & Angelici, R. J. (1999). Synthesis and Technique in Inorganic Chemistry. CA: University Science Books: Mill Valley. ISBN 0935702482.{{cite book}}: CS1 maint: publisher location (link) <a href="0935702482" target="_blank">0935702482</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">Wilkinson, Geoffrey (1963). "Ferrocene". Organic Syntheses; Collected Volumes, vol. 4, p. 473. <a href="/wiki/Geoffrey_Wilkinson" target="_blank">/wiki/Geoffrey_Wilkinson</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">Wilkinson, G.; Birmingham, J. G. (1954). "Bis-cyclopentadienyl Compounds of Ti, Zr, V, Nb and Ta". J. Am. Chem. Soc. 76 (17): 4281–84. Bibcode:1954JAChS..76.4281W. doi:10.1021/ja01646a008. <a href="/wiki/Geoffrey_Wilkinson" target="_blank">/wiki/Geoffrey_Wilkinson</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">Macomber, D. W.; Hart, W. P.; Rausch, M. D. (1982). "Functionally Substituted Cyclopentadienyl Metal Compounds". Adv. Organomet. Chem. Advances in Organometallic Chemistry. 21: 1–55. doi:10.1016/S0065-3055(08)60377-9. ISBN 9780120311217. <a href="9780120311217" target="_blank">9780120311217</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
<li id="fn:12">Petrov, Alex R.; Jess, Kristof; Freytag, Matthias; Jones, Peter G.; Tamm, Matthias (2013). "Large-Scale Preparation of 1,1′-Ferrocenedicarboxylic Acid, a Key Compound for the Synthesis of 1,1′-Disubstituted Ferrocene Derivatives". Organometallics. 32 (20): 5946–5954. doi:10.1021/om4004972. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></li>
<li id="fn:13">Robert E. Dinnebier; Ulrich Behrens & Falk Olbrich (1997). "Solid State Structures of Cyclopentadienyllithium, -sodium, and -potassium. Determination by High-Resolution Powder Diffraction". Organometallics. 16 (17): 3855–3858. doi:10.1021/om9700122. <a href="/wiki/Organometallics" target="_blank">/wiki/Organometallics</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></li>
<li id="fn:14">Elschenbroich, C. (2006). Organometallics. Wiley-VCH: Weinheim. ISBN 978-3-527-29390-2. <a href="978-3-527-29390-2" target="_blank">978-3-527-29390-2</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></li>
<li id="fn:15">Reetz, Manfred T.; Hütte, Stephan; Goddard, Richard (1995-03-01). "Tetrabutylammonium Salts of 2-Nitropropane, Cyclopentadiene and 9-Ethylfluorene: Crystal Structures and Use in Anionic Polymerization". Zeitschrift für Naturforschung B. 50 (3): 415–422. doi:10.1515/znb-1995-0316. ISSN 1865-7117. S2CID 45791403. <a href="https://doi.org/10.1515%2Fznb-1995-0316" target="_blank">https://doi.org/10.1515%2Fznb-1995-0316</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></li>
</ol>

Sodium cyclopentadienide open-in-new

Sodium cyclopentadienide