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Dicobalt octacarbonyl
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<h2 id="synthesis-structure-properties">Synthesis, structure, properties</h2> <p>Dicobalt octacarbonyl an orange-colored, <a href="/facts/Pyrophoric/1b8Sl2AJ">pyrophoric</a> solid.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> It is synthesised by the high pressure <a href="/facts/Carbonylation/Jq8jghNR">carbonylation</a> of cobalt(II) <a href="/facts/Salt_(chemistry)/lsSKwGpn">salts</a>:<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p> 2 (CH3COO)2Co + 8 CO + 2 H2 → Co2(CO)8 + 4 CH3COOH <p>The preparation is often carried out in the presence of <a href="/facts/Cyanide/t0o8FMKI">cyanide</a>, converting the cobalt(II) salt into a <a href="/facts/Pentacyanocobaltate/kIuF5hve">pentacyanocobaltate</a>(II) complex that reacts with carbon monoxide to yield K[Co(CO)4]. Acidification produces <a href="/facts/Cobalt_tetracarbonyl_hydride/6bn7bu2K">cobalt tetracarbonyl hydride</a>, HCo(CO)4, which degrades near room temperature to dicobalt octacarbonyl and hydrogen.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a><a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> It can also be prepared by heating cobalt metal to above 250 °C in a stream of <a href="/facts/Carbon_monoxide/CKuLtEMJ">carbon monoxide</a> gas at about 200 to 300 <a href="/facts/Atmosphere_(unit)/aTbYALII">atm</a>:<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p> 2 Co + 8 CO → Co2(CO)8 <p>It exist as a mixture of rapidly interconverting <a href="/facts/Isomer/PXlvDVdg">isomers</a>.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a><a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> In solution, there are two isomers known that rapidly interconvert:<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p> <p>The major isomer (on the left in the above <a href="/facts/Equilibrium_chemistry/mkjCWwnx">equilibrium</a> process) contains two bridging carbonyl ligands linking the cobalt centres and six terminal carbonyl ligands, three on each metal.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> It can be summarised by the formula (CO)3Co(μ-CO)2Co(CO)3 and has C2v <a href="/facts/Symmetry_group/CNqeseMp">symmetry</a>. This structure resembles <a href="/facts/Diiron_nonacarbonyl/4JEgbeI2">diiron nonacarbonyl</a> (Fe2(CO)9) but with one fewer bridging carbonyl. The Co–Co distance is 2.52 Å, and the Co–COterminal and Co–CObridge distances are 1.80 and 1.90 Å, respectively.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> Analysis of the bonding suggests the absence of a direct cobalt–cobalt bond.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> </p><p>The minor isomer has no bridging carbonyl ligands, but instead has a direct bond between the cobalt centres and eight terminal carbonyl ligands, four on each metal atom.<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> It can be summarised by the formula (CO)4Co-Co(CO)4 and has D4d symmetry. It features an unbridged cobalt–cobalt bond that is 2.70 Å in length in the solid structure when crystallized together with <a href="/facts/Buckminsterfullerene/F0VebtPK">C60</a>.<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> </p> Isomers of dicobalt octacarbonyl <h2 id="reactions">Reactions</h2> <h3>Reduction</h3> <p>Dicobalt octacarbonyl is reductively cleaved by alkali metals and related reagents, such as <a href="/facts/Sodium_amalgam/NlTRR9eq">sodium amalgam</a>. The resulting sodium tetracarbonylcobaltate protonates to give <a href="/facts/Tetracarbonyl_cobalt_hydride/6bn7bu2K">tetracarbonyl cobalt hydride</a>:<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> </p> Co2(CO)8 + 2 Na → 2 Na[Co(CO)4] Na[Co(CO)4] + H+ → H[Co(CO)4] + Na+ <p>Salts of this form are also intermediates in the cyanide synthesis pathway for dicobalt octacarbonyl.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a> </p> <h3>Reactions with electrophiles</h3> <p>Halogens and related reagents cleave the Co–Co bond to give pentacoordinated halotetracarbonyls: </p> Co2(CO)8 + Br2 → 2 Br[Co(CO)4] <p><a href="/facts/Cobalt_tricarbonyl_nitrosyl/Q9PJYfyJ">Cobalt tricarbonyl nitrosyl</a> is produced by treatment of dicobalt octacarbonyl with nitric oxide: </p> Co2(CO)8 + 2 NO → 2 Co(CO)3NO + 2 CO <h3>Reactions with alkynes</h3> <p>The <a href="/facts/Nicholas_reaction/rjEpFWBJ">Nicholas reaction</a> is a <a href="/facts/Substitution_reaction/zpqsbWAo">substitution reaction</a> whereby an alkoxy group located on the α-carbon of an <a href="/facts/Alkyne/VHI4N5Wo">alkyne</a> is replaced by another <a href="/facts/Nucleophile/xYccoaJQ">nucleophile</a>. The alkyne reacts first with dicobalt octacarbonyl, from which is generated a stabilized <a href="/facts/Propargyl/8G5fQUa9">propargylic</a> <a href="/facts/Cation/wrbwhF3z">cation</a> that reacts with the incoming nucleophile and the product then forms by oxidative demetallation.<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a><a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a> </p> <p>The <a href="/facts/Pauson%E2%80%93Khand_reaction/B6hSchrb">Pauson–Khand reaction</a>,<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a> in which an <a href="/facts/Alkyne/VHI4N5Wo">alkyne</a>, an alkene, and carbon monoxide cyclize to give a <a href="/facts/Cyclopentenone/gRWxxY78">cyclopentenone</a>, can be catalyzed by Co2(CO)8,<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a><a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a> though newer methods that are more efficient have since been developed:<a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a><a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a> </p> <p>Co2(CO)8 reacts with <a href="/facts/Alkyne/VHI4N5Wo">alkynes</a> to form a stable covalent complex, which is useful as a <a href="/facts/Protective_group/f92hVwHl">protective group</a> for the alkyne. This complex itself can also be used in the Pauson–Khand reaction.<a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> </p><p>Intramolecular Pauson–Khand reactions, where the starting material contains both the alkene and alkyne moieties, are possible. In the <a href="/facts/Asymmetric_synthesis/5hJe37TL">asymmetric synthesis</a> of the <i><a href="/facts/Lycopodium/LhqjEerH">Lycopodium</a></i> <a href="/facts/Alkaloid/m6hUXohz">alkaloid</a> huperzine-Q, Takayama and co-workers used an intramolecular Pauson–Khand reaction to cyclise an <a href="/facts/Enyne/8vK6rK2s">enyne</a> containing a <i>tert</i>-butyldiphenylsilyl (TBDPS) <a href="/facts/Protecting_group/f92hVwHl">protected</a> primary alcohol.<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> The preparation of the cyclic siloxane moiety immediately prior to the introduction of the dicobalt octacarbonyl ensures that the product is formed with the desired <a href="/facts/Conformational_isomerism/JflrT5Ws">conformation</a>.<a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a> </p> <p>Dicobalt octacarbonyl can catalyze <a href="/facts/Alkyne_trimerisation/7pDT3SKB">alkyne trimerisation</a> of <a href="/facts/Diphenylacetylene/d6APXh1A">diphenylacetylene</a> and its derivatives to <a href="/facts/Hexaphenylbenzene/cSs9uuK4">hexaphenylbenzenes</a>.<a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a> Symmetrical diphenylacetylenes form 6-substituted hexaphenylbenzenes, while asymmetrical diphenylacetylenes form a mixture of two isomers.<a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a> </p> <h3>Hydroformylation</h3> <p><a href="/facts/Hydrogenation/l7EzNSA7">Hydrogenation</a> of Co2(CO)8 produces <a href="/facts/Cobalt_tetracarbonyl_hydride/6bn7bu2K">cobalt tetracarbonyl hydride</a> H[Co(CO)4]:<a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a> </p> Co2(CO)8 + H2 → 2 H[Co(CO)4] <p>This hydride is a <a href="/facts/Catalyst/LPBS7TQC">catalyst</a> for <a href="/facts/Hydroformylation/KCnbNIu7">hydroformylation</a> – the conversion of <a href="/facts/Alkene/RtYcS6kU">alkenes</a> to <a href="/facts/Aldehyde/xSIRkW03">aldehydes</a>.<a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a><a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a> The <a href="/facts/Catalytic_cycle/At7x3sNe">catalytic cycle</a> for this hydroformylation is shown in the diagram.<a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a><a class="footnote-ref" id="fnref:36" href="#fn:36"><sup>36</sup></a><a class="footnote-ref" id="fnref:37" href="#fn:37"><sup>37</sup></a> </p> <h3>Substitution reactions</h3> <p>The CO ligands can be replaced with tertiary <a href="/facts/Phosphine/aYysn5TS">phosphine</a> ligands to give Co2(CO)−8<i>x</i>(PR3)<i>x</i>. These bulky derivatives are more selective catalysts for hydroformylation reactions.<a class="footnote-ref" id="fnref:38" href="#fn:38"><sup>38</sup></a> "<a href="/facts/HSAB_theory/yguwscxc">Hard</a>" Lewis bases, e.g. <a href="/facts/Pyridine/X817hCch">pyridine</a>, cause <a href="/facts/Disproportionation/67QMkXrV">disproportionation</a>: </p> 12 C5H5N + 3 Co2(CO)8 → 2 [Co(C5H5N)6][Co(CO)4]2 + 8 CO <h3>Conversion to higher carbonyls</h3> <p>Heating causes decarbonylation and formation of <a href="/facts/Tetracobalt_dodecacarbonyl/XEfg2HDY">tetracobalt dodecacarbonyl</a>:<a class="footnote-ref" id="fnref:39" href="#fn:39"><sup>39</sup></a><a class="footnote-ref" id="fnref:40" href="#fn:40"><sup>40</sup></a> </p> 2 Co2(CO)8 → Co4(CO)12 + 4 CO <p>Like many metal carbonyls, dicobalt octacarbonyl abstracts halides from alkyl halides. Upon reaction with <a href="/facts/Bromoform/jhmbBrtg">bromoform</a>, it converts to <a href="/facts/Methylidynetricobaltnonacarbonyl/Fbcwt8sj">methylidynetricobaltnonacarbonyl</a>, HCCo3(CO)9, by a reaction that can be idealised as:<a class="footnote-ref" id="fnref:41" href="#fn:41"><sup>41</sup></a> </p> 9 Co2(CO)8 + 4 CHBr3 → 4 HCCo3(CO)9 + 36 CO + 6 CoBr2 <h2 id="safety">Safety</h2> <p>Co2(CO)8 a volatile source of cobalt(0), is <a href="/facts/Pyrophoric/1b8Sl2AJ">pyrophoric</a> and releases <a href="/facts/Carbon_monoxide/CKuLtEMJ">carbon monoxide</a> upon decomposition.<a class="footnote-ref" id="fnref:42" href="#fn:42"><sup>42</sup></a> The <a href="/facts/National_Institute_for_Occupational_Safety_and_Health/5WjdDNMN">National Institute for Occupational Safety and Health</a> has <a href="/facts/Recommended_exposure_limit/nexWYeNv">recommended</a> that workers should not be exposed to concentrations greater than 0.1 mg/m3 over an eight-hour time-weighted average, without the proper respiratory gear.<a class="footnote-ref" id="fnref:43" href="#fn:43"><sup>43</sup></a> </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Pauson, Peter L.; Stambuli, James P.; Chou, Teh-Chang; Hong, Bor-Cherng (2014). "Octacarbonyldicobalt". Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. pp. 1–26. doi:10.1002/047084289X.ro001.pub3. ISBN 9780470842898. <a href="9780470842898" target="_blank">9780470842898</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Donaldson, John Dallas; Beyersmann, Detmar (2005). "Cobalt and Cobalt Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a07_281.pub2. ISBN 3527306730. <a href="3527306730" target="_blank">3527306730</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Elschenbroich, C.; Salzer, A. (1992). Organometallics: A Concise Introduction (2nd ed.). Weinheim: Wiley-VCH. ISBN 3-527-28165-7. <a href="3-527-28165-7" target="_blank">3-527-28165-7</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Sweany, Ray L.; Brown, Theodore L. (1977). "Infrared spectra of matrix-isolated dicobalt octacarbonyl. Evidence for the third isomer". Inorganic Chemistry. 16 (2): 415–421. doi:10.1021/ic50168a037. <a href="/wiki/Theodore_L._Brown" target="_blank">/wiki/Theodore_L._Brown</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Gilmont, Paul; Blanchard, Arthur A. (1946). Dicobalt Octacarbonyl, Cobalt Nitrosyl Tricarbonyl, and Cobalt Tetracarbonyl Hydride. Inorganic Syntheses. Vol. 2. pp. 238–243. doi:10.1002/9780470132333.ch76. ISBN 9780470132333. <a href="9780470132333" target="_blank">9780470132333</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Gilmont, Paul; Blanchard, Arthur A. (1946). Dicobalt Octacarbonyl, Cobalt Nitrosyl Tricarbonyl, and Cobalt Tetracarbonyl Hydride. Inorganic Syntheses. Vol. 2. pp. 238–243. doi:10.1002/9780470132333.ch76. ISBN 9780470132333. <a href="9780470132333" target="_blank">9780470132333</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Donaldson, John Dallas; Beyersmann, Detmar (2005). "Cobalt and Cobalt Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a07_281.pub2. ISBN 3527306730. <a href="3527306730" target="_blank">3527306730</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Orchin, Milton (1953). "Hydrogenation of Organic Compounds with Synthesis Gas". Advances in Catalysis. Vol. 5. Academic Press. pp. 385–415. ISBN 9780080565095. <a href="9780080565095" target="_blank">9780080565095</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Donaldson, John Dallas; Beyersmann, Detmar (2005). "Cobalt and Cobalt Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a07_281.pub2. ISBN 3527306730. <a href="3527306730" target="_blank">3527306730</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Pauson, Peter L.; Stambuli, James P.; Chou, Teh-Chang; Hong, Bor-Cherng (2014). "Octacarbonyldicobalt". Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. pp. 1–26. doi:10.1002/047084289X.ro001.pub3. ISBN 9780470842898. <a href="9780470842898" target="_blank">9780470842898</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Donaldson, John Dallas; Beyersmann, Detmar (2005). "Cobalt and Cobalt Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a07_281.pub2. ISBN 3527306730. <a href="3527306730" target="_blank">3527306730</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Sweany, Ray L.; Brown, Theodore L. (1977). "Infrared spectra of matrix-isolated dicobalt octacarbonyl. Evidence for the third isomer". Inorganic Chemistry. 16 (2): 415–421. doi:10.1021/ic50168a037. <a href="/wiki/Theodore_L._Brown" target="_blank">/wiki/Theodore_L._Brown</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Sweany, Ray L.; Brown, Theodore L. (1977). "Infrared spectra of matrix-isolated dicobalt octacarbonyl. Evidence for the third isomer". Inorganic Chemistry. 16 (2): 415–421. doi:10.1021/ic50168a037. <a href="/wiki/Theodore_L._Brown" target="_blank">/wiki/Theodore_L._Brown</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Sumner, G. Gardner; Klug, Harold P.; Alexander, Leroy E. (1964). "The crystal structure of dicobalt octacarbonyl". Acta Crystallographica. 17 (6): 732–742. doi:10.1107/S0365110X64001803. <a href="https://doi.org/10.1107%2FS0365110X64001803" target="_blank">https://doi.org/10.1107%2FS0365110X64001803</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Green, Jennifer C.; Green, Malcolm L. H.; Parkin, Gerard (2012). "The occurrence and representation of three-centre two-electron bonds in covalent inorganic compounds". Chemical Communications. 2012 (94): 11481–11503. doi:10.1039/c2cc35304k. PMID 23047247. <a href="/wiki/Malcolm_Green_(chemist)" target="_blank">/wiki/Malcolm_Green_(chemist)</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Sweany, Ray L.; Brown, Theodore L. (1977). "Infrared spectra of matrix-isolated dicobalt octacarbonyl. Evidence for the third isomer". Inorganic Chemistry. 16 (2): 415–421. doi:10.1021/ic50168a037. <a href="/wiki/Theodore_L._Brown" target="_blank">/wiki/Theodore_L._Brown</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Garcia, Thelma Y.; Fettinger, James C.; Olmstead, Marilyn M.; Balch, Alan L. (2009). "Splendid symmetry: Crystallization of an unbridged isomer of Co2(CO)8 in Co2(CO)8·C60". Chemical Communications. 2009 (46): 7143–7145. doi:10.1039/b915083h. PMID 19921010. <a href="/wiki/Chemical_Communications" target="_blank">/wiki/Chemical_Communications</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>Donaldson, John Dallas; Beyersmann, Detmar (2005). "Cobalt and Cobalt Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a07_281.pub2. ISBN 3527306730. <a href="3527306730" target="_blank">3527306730</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Orchin, Milton (1953). "Hydrogenation of Organic Compounds with Synthesis Gas". Advances in Catalysis. Vol. 5. Academic Press. pp. 385–415. ISBN 9780080565095. <a href="9780080565095" target="_blank">9780080565095</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Nicholas, Kenneth M. (1987). "Chemistry and synthetic utility of cobalt-complexed propargyl cations". Acc. Chem. Res. (Review). 20 (6): 207–214. doi:10.1021/ar00138a001. <a href="/wiki/Acc._Chem._Res." target="_blank">/wiki/Acc._Chem._Res.</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>Teobald, Barry J. (2002). "The Nicholas reaction: The use of dicobalt hexacarbonyl-stabilised propargylic cations in synthesis". Tetrahedron (Review). 58 (21): 4133–4170. doi:10.1016/S0040-4020(02)00315-0. <a href="/wiki/Tetrahedron_(journal)" target="_blank">/wiki/Tetrahedron_(journal)</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>Pauson, P. L.; Khand, I. U. (1977). "Uses of Cobalt-Carbonyl Acetylene Complexes in Organic Synthesis". Ann. N. Y. Acad. Sci. 295 (1): 2–14. Bibcode:1977NYASA.295....2P. doi:10.1111/j.1749-6632.1977.tb41819.x. S2CID 84203764. <a href="/wiki/Peter_Pauson" target="_blank">/wiki/Peter_Pauson</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>Donaldson, John Dallas; Beyersmann, Detmar (2005). "Cobalt and Cobalt Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a07_281.pub2. ISBN 3527306730. <a href="3527306730" target="_blank">3527306730</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>Blanco-Urgoiti, Jaime; Añorbe, Loreto; Pérez-Serrano, Leticia; Domínguez, Gema; Pérez-Castells, Javier (2004). "The Pauson–Khand reaction, a powerful synthetic tool for the synthesis of complex molecules". Chem. Soc. Rev. 33 (1): 32–42. doi:10.1039/b300976a. PMID 14737507. <a href="/wiki/Chem._Soc._Rev." target="_blank">/wiki/Chem._Soc._Rev.</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>Schore, Neil E. (1991). "The Pauson–Khand Cycloaddition Reaction for Synthesis of Cyclopentenones". Org. React. 40: 1–90. doi:10.1002/0471264180.or040.01. ISBN 0471264180. <a href="0471264180" target="_blank">0471264180</a> <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> <li id="fn:26"><p>Gibson, Susan E.; Stevenazzi, Andrea (2003). "The Pauson–Khand Reaction: The Catalytic Age Is Here!". Angew. Chem. Int. Ed. 42 (16): 1800–1810. doi:10.1002/anie.200200547. PMID 12722067. <a href="/wiki/Angew._Chem._Int._Ed." target="_blank">/wiki/Angew._Chem._Int._Ed.</a> <a href="#fnref:26" class="footnote-back-ref">↩</a></p></li> <li id="fn:27"><p>Pauson, P. L.; Khand, I. U. (1977). "Uses of Cobalt-Carbonyl Acetylene Complexes in Organic Synthesis". Ann. N. Y. Acad. Sci. 295 (1): 2–14. Bibcode:1977NYASA.295....2P. doi:10.1111/j.1749-6632.1977.tb41819.x. S2CID 84203764. <a href="/wiki/Peter_Pauson" target="_blank">/wiki/Peter_Pauson</a> <a href="#fnref:27" class="footnote-back-ref">↩</a></p></li> <li id="fn:28"><p>Nakayama, Atsushi; Kogure, Noriyuki; Kitajima, Mariko; Takayama, Hiromitsu (2011). "Asymmetric Total Synthesis of a Pentacyclic Lycopodium Alkaloid: Huperzine-Q". Angew. Chem. Int. Ed. 50 (35): 8025–8028. doi:10.1002/anie.201103550. PMID 21751323. <a href="/wiki/Angew._Chem._Int._Ed." target="_blank">/wiki/Angew._Chem._Int._Ed.</a> <a href="#fnref:28" class="footnote-back-ref">↩</a></p></li> <li id="fn:29"><p>Ho, Tse-Lok (2016). "Dicobalt Octacarbonyl". Fiesers' Reagents for Organic Synthesis. Vol. 28. John Wiley & Sons. pp. 251–252. ISBN 9781118942819. <a href="9781118942819" target="_blank">9781118942819</a> <a href="#fnref:29" class="footnote-back-ref">↩</a></p></li> <li id="fn:30"><p>Vij, V.; Bhalla, V.; Kumar, M. (8 August 2016). "Hexaarylbenzene: Evolution of Properties and Applications of Multitalented Scaffold". Chemical Reviews. 116 (16): 9565–9627. doi:10.1021/acs.chemrev.6b00144. <a href="/wiki/Chemical_Reviews" target="_blank">/wiki/Chemical_Reviews</a> <a href="#fnref:30" class="footnote-back-ref">↩</a></p></li> <li id="fn:31"><p>Xiao, W.; Feng, X.; Ruffieux, P.; Gröning, O.; Müllen, K.; Fasel, R. (18 June 2008). "Self-Assembly of Chiral Molecular Honeycomb Networks on Au(111)". Journal of the American Chemical Society. 130 (28): 8910–8912. doi:10.1021/ja7106542. <a href="/wiki/Journal_of_the_American_Chemical_Society" target="_blank">/wiki/Journal_of_the_American_Chemical_Society</a> <a href="#fnref:31" class="footnote-back-ref">↩</a></p></li> <li id="fn:32"><p>Pfeffer, M.; Grellier, M. (2007). "Cobalt Organometallics". Comprehensive Organometallic Chemistry III. Vol. 7. Elsevier. pp. 1–119. doi:10.1016/B0-08-045047-4/00096-0. ISBN 9780080450476. <a href="9780080450476" target="_blank">9780080450476</a> <a href="#fnref:32" class="footnote-back-ref">↩</a></p></li> <li id="fn:33"><p>Elschenbroich, C.; Salzer, A. (1992). Organometallics: A Concise Introduction (2nd ed.). Weinheim: Wiley-VCH. ISBN 3-527-28165-7. <a href="3-527-28165-7" target="_blank">3-527-28165-7</a> <a href="#fnref:33" class="footnote-back-ref">↩</a></p></li> <li id="fn:34"><p>Pfeffer, M.; Grellier, M. (2007). "Cobalt Organometallics". Comprehensive Organometallic Chemistry III. Vol. 7. Elsevier. pp. 1–119. doi:10.1016/B0-08-045047-4/00096-0. ISBN 9780080450476. <a href="9780080450476" target="_blank">9780080450476</a> <a href="#fnref:34" class="footnote-back-ref">↩</a></p></li> <li id="fn:35"><p>Elschenbroich, C.; Salzer, A. (1992). Organometallics: A Concise Introduction (2nd ed.). Weinheim: Wiley-VCH. ISBN 3-527-28165-7. <a href="3-527-28165-7" target="_blank">3-527-28165-7</a> <a href="#fnref:35" class="footnote-back-ref">↩</a></p></li> <li id="fn:36"><p>Heck, Richard F.; Breslow, David S. (1961). "The Reaction of Cobalt Hydrotetracarbonyl with Olefins". Journal of the American Chemical Society. 83 (19): 4023–4027. doi:10.1021/ja01480a017. <a href="/wiki/Richard_F._Heck" target="_blank">/wiki/Richard_F._Heck</a> <a href="#fnref:36" class="footnote-back-ref">↩</a></p></li> <li id="fn:37"><p>Halpern, Jack (2001). "Organometallic chemistry at the threshold of a new millennium. Retrospect and prospect". Pure and Applied Chemistry. 73 (2): 209–220. doi:10.1351/pac200173020209. <a href="/wiki/Jack_Halpern_(chemist)" target="_blank">/wiki/Jack_Halpern_(chemist)</a> <a href="#fnref:37" class="footnote-back-ref">↩</a></p></li> <li id="fn:38"><p>Donaldson, John Dallas; Beyersmann, Detmar (2005). "Cobalt and Cobalt Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a07_281.pub2. ISBN 3527306730. <a href="3527306730" target="_blank">3527306730</a> <a href="#fnref:38" class="footnote-back-ref">↩</a></p></li> <li id="fn:39"><p>Donaldson, John Dallas; Beyersmann, Detmar (2005). "Cobalt and Cobalt Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a07_281.pub2. ISBN 3527306730. <a href="3527306730" target="_blank">3527306730</a> <a href="#fnref:39" class="footnote-back-ref">↩</a></p></li> <li id="fn:40"><p>Chini, P. (1968). "The closed metal carbonyl clusters". Inorganica Chimica Acta Reviews. 2: 31–51. doi:10.1016/0073-8085(68)80013-0. <a href="/w/index.php?title=Inorganica_Chimica_Acta_Reviews&action=edit&redlink=1" target="_blank">/w/index.php?title=Inorganica_Chimica_Acta_Reviews&action=edit&redlink=1</a> <a href="#fnref:40" class="footnote-back-ref">↩</a></p></li> <li id="fn:41"><p>Nestle, Mara O.; Hallgren, John E.; Seyferth, Dietmar; Dawson, Peter; Robinson, Brian H. (2007). "μ3-Methylidyne and μ3-Benzylidyne-Tris(Tricarbonylcobalt)". Inorg. Synth. 20: 226–229. doi:10.1002/9780470132517.ch53. ISBN 9780470132517. <a href="9780470132517" target="_blank">9780470132517</a> <a href="#fnref:41" class="footnote-back-ref">↩</a></p></li> <li id="fn:42"><p>Cole Parmer MSDS <a href="http://www.coleparmer.com/catalog/Msds/56919.htm" target="_blank">http://www.coleparmer.com/catalog/Msds/56919.htm</a> <a href="#fnref:42" class="footnote-back-ref">↩</a></p></li> <li id="fn:43"><p>CDC - NIOSH Pocket Guide to Chemical Hazards <a href="https://www.cdc.gov/niosh/npg/npgd0147.html" target="_blank">https://www.cdc.gov/niosh/npg/npgd0147.html</a> <a href="#fnref:43" class="footnote-back-ref">↩</a></p></li> </ol>