| Revision as of 11:15, 21 October 2011 editBeetstra (talk | contribs)Edit filter managers, Administrators172,031 edits Script assisted update of identifiers for the Chem/Drugbox validation project (updated: 'ChEBI').← Previous edit |
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{{chembox |
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{{chembox |
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| Verifiedfields = changed |
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| verifiedrevid = 396315476 |
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| Watchedfields = changed |
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| ImageFileL1 = Cobaltocene.png |
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| verifiedrevid = 456661727 |
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| ImageFileL1 = Cobaltocene.svg |
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| ImageSizeL1 = 100px |
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| ImageSizeL1 = 100px |
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| ImageNameL1 = Skeletal formula of cobaltocene |
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| ImageNameL1 = Skeletal formula of cobaltocene |
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| ImageFileR1 = Cobaltocene-3D-balls.png |
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| ImageFileR1 = Cobaltocene-3D-balls.png |
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| ImageSizeR1 = 150px |
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| ImageSizeR1 = 150px |
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| ImageNameR1 = Ball-and-stick model of cobaltocene |
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| ImageNameR1 = Ball-and-stick model of cobaltocene |
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| IUPACName = cobaltocene,<br/>bis(η<sup>5</sup>- cyclopentadienyl)-<br />cobalt |
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| IUPACName = Cobaltocene<br/>Bis(''η''<sup>5</sup>-cyclopentadienyl)cobalt |
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| OtherNames = Cp<sub>2</sub>Co |
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| OtherNames = Cp<sub>2</sub>Co |
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| Section1 = {{Chembox Identifiers |
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|Section1={{Chembox Identifiers |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID = 83848 |
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| ChemSpiderID = 83848 |
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| InChI = 1/2C5H5.Co/c2*1-2-4-5-3-1;/h2*1-5H;/q2*-1;+2 |
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| InChI = 1/2C5H5.Co/c2*1-2-4-5-3-1;/h2*1-5H;/q2*-1;+2 |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo = 1277-43-6 |
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| CASNo = 1277-43-6 |
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| ChEBI_Ref = {{ebicite|correct|EBI}} |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| UNII = 4W7LGU89CV |
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| ChEBI = <!-- blanked - oldvalue: 30678 --> |
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| ChEBI_Ref = {{ebicite|changed|EBI}} |
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| EINECS = |
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| RTECS = GG0350000 |
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| ChEBI = 30678 |
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| EINECS = 215-061-0 |
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| RTECS = GG0350000 |
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| PubChem = 22045960 |
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}} |
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| Section2 = {{Chembox Properties |
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|Section2={{Chembox Properties |
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| Formula = |
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| Formula = |
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| MolarMass = 189.12 g/mol |
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| MolarMass = 189.12 g/mol |
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| Appearance = |
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| Appearance = Dark purple solid |
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| Density = |
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| Density = |
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| Solubility = not soluble |
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| Solubility = Insoluble |
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| MeltingPt = |
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| MeltingPtC = 171-173 |
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| BoilingPt = |
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| BoilingPt = |
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}} |
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| Section3 = {{Chembox Structure |
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|Section3={{Chembox Structure |
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| Coordination = sandwich |
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| Coordination = sandwich |
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| Dipole = zero |
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| Dipole = zero |
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}} |
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| Section4 = {{Chembox Thermochemistry |
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|Section4={{Chembox Thermochemistry |
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| DeltaHf = +237 kJ/mol (uncertain) |
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| DeltaHf = +237 kJ/mol (uncertain) |
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| DeltaHc = -5839 kJ/mol |
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| DeltaHc = −5839 kJ/mol |
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| Entropy = 236 J.K<sup>−1</sup>.mol<sup>−1</sup> |
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| Entropy = 236 J K<sup>−1</sup> mol<sup>−1</sup> |
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}} |
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| Section7 = {{Chembox Hazards |
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|Section7={{Chembox Hazards |
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| ExternalSDS = |
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| EUClass = {{Hazchem Xi}} |
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| GHSPictograms = {{GHS02}}{{GHS08}}<ref name=sds>{{cite web|title = Bis(cyclopentadienyl)cobalt(II)|url = https://www.americanelements.com/bis-cyclopentadienyl-cobalt-ii-1277-43-6|publisher = ]|accessdate = 2018-08-24}}</ref> |
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| RPhrases = {{R10}}, {{R36/37/38}} |
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| GHSSignalWord = Danger<ref name=sds /> |
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| SPhrases = {{S9}}, {{S16}}, {{S26}}, {{S33}}, {{S37/39}} |
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| HPhrases = {{H-phrases|228|317|351}}<ref name=sds /> |
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| NFPA-H = 1 |
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| PPhrases = {{P-phrases|210|261|280|363|405|501}}<ref name=sds /> |
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| NFPA-F = 2 |
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| NFPA-R = 0 |
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| NFPA-H = 1 |
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| NFPA-F = 2 |
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| NFPA-R = 0 |
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}} |
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}} |
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| Section8 = {{Chembox Related |
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|Section8={{Chembox Related |
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| Function = ]s |
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| OtherFunction_label = ]s |
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| OtherFunctn = ]<br />]<br />]}} |
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| OtherFunction = ]<br />]<br />]}} |
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'''Cobaltocene''', known also as '''bis(cyclopentadienyl)cobalt(II)''' or even "bis Cp cobalt", is an ] with the formula Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>. It is a dark purple solid that sublimes readily slightly above room temperature. Cobaltocene was discovered shortly after ], the first ]. Due to the ease with which it reacts with O<sub>2</sub>, the compound must be handled and stored using ]s. |
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'''Cobaltocene''', known also as '''bis(cyclopentadienyl)cobalt(II)''' or even "bis Cp cobalt", is an ] with the formula Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>. It is a dark purple solid that sublimes readily slightly above room temperature. Cobaltocene was discovered shortly after ], the first ]. Due to the ease with which it reacts with oxygen, the compound must be handled and stored using ]s. |
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==Synthesis== |
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==Synthesis== |
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] |
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Cobaltocene is prepared by the reaction of ] (NaC<sub>5</sub>H<sub>5</sub>) with anhydrous ] in ] solution. Sodium chloride is cogenerated, and the ] product is usually purified by ].<ref name=King>King, R. B. “Organometallic Syntheses” Volume 1: Academic Press: New York, 1965.</ref> |
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Cobaltocene is prepared by the reaction of ] (NaC<sub>5</sub>H<sub>5</sub>) with anhydrous ] in ] solution. Sodium chloride is cogenerated, and the ] product is usually purified by ].<ref name=King>{{cite book|last=King|first= R. B. |title=Organometallic Syntheses|volume=1|publisher= Academic Press|location=New York, NY|date=1965}}</ref> |
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==Structure and bonding== |
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==Structure and bonding== |
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In Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> the Co centre is "sandwiched" between two ] (Cp) rings. The Co-C bond lengths are about 2.1 Å, slightly longer than the Fe-C bond in ferrocene.<ref>M. Yu. Antipin, R. Boese, N. Augart, G. Schmid "Redetermination of the cobaltocene crystal structure at 100 K and 297 K: Comparison with ferrocene and nickelocene" Structural Chemistry 1993, Volume 4, Number 2, 91-101. {{DOI|10.1007/BF00677370}}</ref> |
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In Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> the Co centre is "sandwiched" between two ] (Cp) rings. The Co–C bond lengths are about 2.1 Å, slightly longer than the Fe–C bond in ferrocene.<ref>{{cite journal|first1=M. Yu. |last1=Antipin|first2= R. |last2=Boese|first3= N. |last3=Augart|first4= G.|last4= Schmid |title=Redetermination of the cobaltocene crystal structure at 100 K and 297 K: Comparison with ferrocene and nickelocene |journal=]|date= 1993 |volume=4 |issue=2 |pages=91–101|doi=10.1007/BF00677370|s2cid=93871667 }}</ref> |
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Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> belongs to a group of organometallic compounds called ]s or sandwich compounds.<ref>C. Elschenbroich, A. Salzer ”Organometallics : A Concise Introduction” (2nd Ed) (1992) from Wiley-VCH: Weinheim. ISBN 3-527-28165-7</ref>Cobaltocene has 19 valence electrons, one more than usually found in organotransition metal complexes, such as its very stable relative ferrocene. (See ].) This additional electron occupies an orbital that is antibonding with respect to the Co-C bonds. Consequently, the Co-C distances are slightly longer than the Fe-C bonds in ferrocene. Many chemical reactions of Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> are characterized by its tendency lose this "extra" electron, yielding 18-electron cation known as cobaltocenium: |
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Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> belongs to a group of organometallic compounds called ]s or sandwich compounds.<ref>{{cite book|first1=C. |last1=Elschenbroich |first2=A. |last2=Salzer |title=Organometallics: A Concise Introduction|edition=2nd |date=1992 |publisher=Wiley-VCH |location=Weinheim |isbn= 978-3-527-28165-7}}</ref> Cobaltocene has 19 valence electrons, one more than usually found in organotransition metal complexes such as its very stable relative ferrocene. (See ].) This additional electron occupies an orbital that is antibonding with respect to the Co–C bonds. Consequently, the Co–C distances are slightly longer than the Fe–C bonds in ferrocene. Many chemical reactions of Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> are characterized by its tendency to lose this "extra" electron, yielding an 18-electron cation known as cobaltocenium: |
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:<chem>\underbrace{2Co(C5H5)2}_{19e-} |
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+ I2 |
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:{| |
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-> |
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\underbrace{2Co(C5H5)2+}_{18e-} |
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+ 2I- |
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</chem> |
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The otherwise close relative of cobaltocene, ] does not exist as a monomer, but spontaneously dimerizes by formation of a C–C bond between Cp rings. |
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==Reactions== |
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===Redox properties=== |
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Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> is a common one-electron reducing agent in the laboratory.<ref>{{cite journal | first1= N. G.|last1= Connelly|first2= W. E.|last2= Geiger | title = Chemical Redox Agents for Organometallic Chemistry | journal = ] | year = 1996 | volume = 96 | pages = 877–910 | doi = 10.1021/cr940053x | pmid=11848774 | issue = 2}}</ref> In fact, the reversibility of the Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> ] couple is so well-behaved that Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> may be used in ] as an ]. Its permethylated analogue ] (Co(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>) is an especially powerful reducing agent, due to inductive donation of electron density from the 10 methyl groups, prompting the cobalt to give up its "extra" electron even more so. These two compounds are rare examples of reductants that dissolve in non-polar organic solvents. The ]s of these compounds follow, using the ferrocene-] couple as the reference: |
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{| class="wikitable" |
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! ] !! ''E''<sup>0</sup> (V) |
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| 2Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> |
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| {{chem|Fe(C|5|H|5|)|2|+}} + e<sup>−</sup> ⇌ Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> || 0.00 (by definition) |
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| + I<sub>2</sub> |
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| 2<sup>+</sup> |
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| + 2I<sup>−</sup> |
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| {{chem|Fe(C|5|Me|5|)|2|+}} + e<sup>−</sup> ⇌ Fe(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub> || −0.59 |
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|<center>19e<sup>−</sup></center> |
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|<center>18e<sup>−</sup></center> |
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| {{chem|Co(C|5|H|5|)|2|+}} + e<sup>−</sup> ⇌ Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> || −1.33 |
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| {{chem|Co(C|5|Me|5|)|2|+}} + e<sup>−</sup> ⇌ Co(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>|| −1.94 |
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</div> |
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The data show that the decamethyl compounds are around 600 mV more reducing than the parent metallocenes. This substituent effect is, however, overshadowed by the influence of the metal: changing from Fe to Co renders the reduction more favorable by over 1.3 volts. |
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The otherwise close relative of cobaltocene, ] does not exist as a monomer, but spontaneously dimerizes by formation of a C-C bond between Cp rings. |
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==Reactions== |
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===Carbonylation=== |
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Treatment of Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> with ] gives the cobalt(I) derivative ], concomitant with loss of one Cp ligand. This conversion is conducted near 130 °C with 500 psi of CO.<ref name=King/><ref>{{cite book |doi=10.1002/9780470132388.ch31|title=Cyclopentadienyl Metal Carbonyls and Some Derivatives|series=Inorganic Syntheses|year=1967|last1=King|first1=R. B.|last2=Stone|first2=F. G. A.|volume=7|pages=99–115|isbn=9780470132388}}</ref> |
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===Redox properties=== |
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Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> is a common one-electron reducing agent in the laboratory.<ref>{{cite journal | author = N. G. Connelly, W. E. Geiger | title = Chemical Redox Agents for Organometallic Chemistry | journal = ] | year = 1996 | volume = 96 | pages = 877–910 | doi = 10.1021/cr940053x | pmid=11848774 | issue = 2}}</ref> In fact, the reversibility of the Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> ] couple is so well behaved that Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> may be used in ] as an ]. Its permethylated analogue ] (Co(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>) is an especially powerful reducing agent, due to inductive donation of electron density from the 10 methyl groups, prompting the cobalt to give up its "extra" electron even more so. These two compounds are rare examples of reductants that dissolve in non-polar organic solvents. The reduction potentials of these compounds follow, using the ferrocene-] couple as the reference: |
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<div align=left> |
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:Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub><sup>+</sup>/Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>: 0 V |
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:Fe(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub><sup>+</sup>/Fe(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>: -0.59 |
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:Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub><sup>+</sup>/Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>: -1.33 |
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:Co(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub><sup>+</sup>/Co(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>: -1.94 |
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</div> |
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The data show that the decamethyl compounds are ca. 600 mV more reducing than the parent metallocenes. This substituent effect is, however, overshadowed by the influence of the metal: changing from Fe to Co renders the reduction more favorable by over 1.3 volts. |
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==Carbonylation== |
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==See also== |
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*] |
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Treatment of Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> with ] gives the cobalt(I) derivative ], concomitant with loss of one Cp ligand.<ref name=King/> |
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==References== |
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==References== |
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==External links== |
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{{Cyclopentadienide complexes}} |
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