| Revision as of 23:20, 9 March 2011 editCheMoBot (talk | contribs)Bots141,565 edits Updating {{chembox}} (no changed fields - added verified revid - updated 'UNII_Ref', 'ChemSpiderID_Ref', 'StdInChI_Ref', 'StdInChIKey_Ref', 'ChEMBL_Ref', 'KEGG_Ref') per Chem/Drugbox validation (← Previous edit |
Latest revision as of 08:30, 14 December 2024 edit undoCitation bot (talk | contribs)Bots5,390,053 edits Added bibcode. | Use this bot. Report bugs. | Suggested by Pancho507 | Linked from User:Pancho507/sandbox/2 | #UCB_webform_linked 3639/3850 |
| (101 intermediate revisions by 49 users not shown) |
| Line 1: |
Line 1: |
|
{{chembox |
|
{{chembox |
|
|
|Verifiedfields = changed |
| ⚫ |
| verifiedrevid = 411821920 |
|
|
|
|Watchedfields = changed |
|
| Name = Pentamethylcyclopentadiene |
|
|
⚫ |
|verifiedrevid = 418038654 |
|
| ImageFile = Pentamethylcyclopentadiene.png |
|
|
|
|Name = Pentamethylcyclopenytadiene |
| ⚫ |
| ImageSize = 120px |
|
|
|
|ImageFile = Pentamethylcyclopentadien.svg |
|
| ImageName = Pentamethylcyclopentadiene |
|
|
⚫ |
|ImageSize = 135 |
| ⚫ |
| Section1 = {{Chembox Identifiers |
|
|
|
|ImageAlt = Skeletal formula of pentamethylcyclopentadiene |
| ⚫ |
| CASNo = 4045-44-7 |
|
|
|
|ImageFile1 = Pentamethylcyclopentadiene molecule ball.png |
| ⚫ |
| SMILES = CC1=C(C)C(C)C(C)=C1C |
|
|
|
|ImageSize1 = 160 |
| ⚫ |
}} |
|
|
|
|ImageAlt1 = Ball-and-stick model of the pentamethylcyclopentadiene molecule |
| ⚫ |
| Section2 = {{Chembox Properties |
|
|
|
|PIN = 1,2,3,4,5-Pentamethylcyclopenta-1,3-diene |
|
| Formula = C<sub>10</sub>H<sub>16</sub> |
|
|
⚫ |
|Section1={{Chembox Identifiers |
|
| MolarMass = 136.24 g/mol |
|
|
|
|CASNo_Ref = {{cascite|correct|??}} |
| ⚫ |
| Solubility = Sparingly soluble |
|
|
⚫ |
|CASNo = 4045-44-7 |
|
| BoilingPt = 55–60 °C (13 mm Hg) |
|
|
|
| UNII_Ref = {{fdacite|correct|FDA}} |
| ⚫ |
}} |
|
|
|
| UNII = DSE3MRZ77C |
| ⚫ |
| Section7 = {{Chembox Hazards |
|
|
⚫ |
|SMILES = CC1=C(C)C(C)C(C)=C1C |
|
| FlashPt = 114 °C |
|
|
|
|PubChem = 77667 |
| ⚫ |
}} |
|
|
|
|ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}} |
|
|
|ChemSpiderID = 70069 |
|
|
|InChI = 1/C10H16/c1-6-7(2)9(4)10(5)8(6)3/h6H,1-5H3 |
|
|
|InChIKey = WQIQNKQYEUMPBM-UHFFFAOYAI |
|
|
|StdInChI_Ref = {{stdinchicite|changed|chemspider}} |
|
|
|StdInChI = 1S/C10H16/c1-6-7(2)9(4)10(5)8(6)3/h6H,1-5H3 |
|
|
|StdInChIKey_Ref = {{stdinchicite|changed|chemspider}} |
|
|
|StdInChIKey = WQIQNKQYEUMPBM-UHFFFAOYSA-N |
|
⚫ |
}} |
|
⚫ |
|Section2={{Chembox Properties |
|
|
|C=10|H=16 |
|
|
|Appearance = Colorless liquid<ref name=pubchem>{{cite web | url=https://pubchem.ncbi.nlm.nih.gov/compound/1_2_3_4_5-Pentamethylcyclopentadiene | title=1,2,3,4,5-Pentamethylcyclopentadiene }}</ref> |
|
|
|Odor = Mild<ref name=pubchem></ref> |
|
|
|Density = 0.87 g/cm<sup>3</sup><ref name=sigmaaldrich>https://www.sigmaaldrich.com/GB/en/sds/aldrich/214027 {{Bare URL inline|date=August 2024}}</ref> |
|
⚫ |
|Solubility = Sparingly soluble |
|
|
|BoilingPtC = 55 to 60 |
|
|
|BoilingPt_notes = at {{convert|13|mmHg|kPa|abbr=on}} |
|
⚫ |
}} |
|
⚫ |
|Section7={{Chembox Hazards |
|
|
|MainHazards = ] |
|
|
|GHSSignalWord = Warning |
|
|
|GHSPictograms = {{GHS02}} |
|
|
|HPhrases = {{H-phrases|H226}} |
|
|
|FlashPtC = 114 |
|
⚫ |
}} |
|
}} |
|
}} |
|
|
|
|
|
'''1,2,3,4,5-Pentamethylcyclopentadiene''' is a cyclic ] with the formula C<sub>5</sub>Me<sub>5</sub>H (Me = CH<sub>3</sub>).<ref>Overview of Cp* Compounds: Elschenbroich, C. and Salzer, A. Organometallics: a Concise Introduction (1989) p. 47</ref> 1,2,3,4,5-Pentamethylcyclopentadiene is the precursor to the ] ''1,2,3,4,5-pentamethylcyclopentadienyl,'' which is often denoted as Cp* (to signify the five methyl groups radiating from the periphery of this ligand as in a five-pointed star). In contrast to less substituted cyclopentadiene derivatives, Cp*H is not prone to dimerization. |
|
'''1,2,3,4,5-Pentamethylcyclopentadiene''' is a ] ] with the formula {{chem2|C5(CH3)5H}}, often written {{chem2|C5Me5H}}, where Me is ].<ref>{{cite book|last1=Elschenbroich |first1=C. |last2=Salzer |first2=A. |title=Organometallics: A Concise Introduction |date=1989 |page=47 |isbn=9783527278183| publisher=]}}</ref> It is a colorless liquid.<ref name=pubchem></ref> |
|
|
|
|
|
1,2,3,4,5-Pentamethylcyclopentadiene is the precursor to the ] ''1,2,3,4,5-pentamethylcyclopentadienyl'', which is often denoted '''Cp*''' ({{chem2|C5Me5}}) and read as "C P star", the "star" signifying the five methyl groups radiating from the core of the ligand. Thus, the 1,2,3,4,5-pentamethylcyclopentadiene's formula is also written Cp*H. In contrast to less-substituted ] derivatives, Cp*H is not prone to dimerization. |
|
|
|
|
|
==Synthesis== |
|
==Synthesis== |
|
Pentamethylcyclopentadiene is commercially available. It was first prepared from ] via 2,3,4,5-tetramethylcyclopent-2-enone.<ref>{{cite journal | author = L. de Vries | title= Preparation of 1,2,3,4,5-Pentamethyl-cyclopentadiene, 1,2,3,4,5,5-Hexamethyl-cyclopentadiene, and 1,2,3,4,5-Pentamethyl-cyclopentadienylcarbinol | journal = ] | volume = 25 | year = 1960 | pages = 1838 | doi = 10.1021/jo01080a623}}</ref> Alternatively 2-butenyllithium adds to ethylacetate followed by acid-catalyzed dehydrocyclization:<ref>{{OrgSynth | author = S. Threlkel, J. E. Bercaw, P. F. Seidler, J. M. Stryker, R. G. Bergman | prep = cv8p0505 | title = 1,2,3,4,5-Pentamethylcyclopentadiene | collvol = 8 | collvolpages = 505 | year = 1993}}</ref><ref>{{cite journal | author = Fendrick, C. M.; Schertz, L. D.; Mintz, E. A.; Marks, T. J. | title = Large-Scale Synthesis of 1,2,3,4,5-Pentamethylcyclopentadiene | journal = ] | volume = 29 | pages = 193–198 | year = 1992 | doi = 10.1002/9780470132609.ch47}}</ref> |
|
Pentamethylcyclopentadiene is commercially available. It was first prepared from ] and 2-butenyllithium, via 2,3,4,5-tetramethylcyclopent-2-enone, with a ] as a key step.<ref>{{cite journal | first= L. |last=De Vries | title= Preparation of 1,2,3,4,5-Pentamethyl-cyclopentadiene, 1,2,3,4,5,5-Hexamethyl-cyclopentadiene, and 1,2,3,4,5-Pentamethyl-cyclopentadienylcarbinol | journal = ] | volume = 25 | year = 1960 | pages = 1838 | doi = 10.1021/jo01080a623 | issue = 10}}</ref> |
|
|
|
|
|
:] |
|
|
|
|
|
Alternatively, 2-butenyllithium adds to ] followed by acid-catalyzed dehydrocyclization:<ref>{{OrgSynth | first1= S. |last1=Threlkel |first2=J. E. |last2=Bercaw |first3=P. F. |last3=Seidler |first4=J. M. |last4=Stryker |first5=R. G. |last5=Bergman | prep = cv8p0505 | title = 1,2,3,4,5-Pentamethylcyclopentadiene | collvol = 8 | collvolpages = 505 | year = 1993}}</ref><ref>{{cite book | last1= Fendrick |first1=C. M. |last2=Schertz |first2=L. D. |last3=Mintz|first3=E. A. |last4=Marks |first4=T. J. |chapter=Large-Scale Synthesis of 1,2,3,4,5-Penta-Methylcyclopentadiene | title = Inorganic Syntheses | volume = 29 | pages = 193–198 | year = 1992 | doi = 10.1002/9780470132609.ch47 | isbn = 978-0-470-13260-9}}</ref> |
|
|
|
|
:MeCH=C(Li)Me + MeC(O)OEt → (MeCH=C(Me))<sub>2</sub>C(OLi)Me + LIOEt |
|
|
|
:] |
| ⚫ |
:(MeCH=C(Me))<sub>2</sub>C(OLi)Me + H<sup>+</sup> → Cp*H + H<sub>2</sub>O + Li<sup>+</sup> |
|
|
|
|
|
|
:] |
|
|
|
|
|
==Organometallic derivatives== |
|
==Organometallic derivatives== |
|
⚫ |
{| class="toccolours floatleft" border="1" style="border-collapse: collapse;" |
|
Cp*H is an important precursor to ] compounds arising from the binding of the five ring-carbon atoms in C<sub>5</sub>Me<sub>5</sub><sup>-</sup>, or Cp*<sup>-</sup>, to metals.<ref>Yamamoto, A. Organotransition Metal Chemistry: Fundamental Concepts and Applications. (1986) p. 105 |
|
|
|
! {{Chemical datatable header}} | Cp*–metal complexes |
|
</ref> |
|
|
===Synthesis of Cp* complexes=== |
|
| ⚫ |
{| class="toccolours" border="1" style="float: right; clear: right; margin: 0 0 1em 1em; border-collapse: collapse;" |
|
|
! {{chembox header}} | Cp*-metal Complexes |
|
|
|- |
|
|- |
|
| Cp*<sub>2</sub>Fe |
|
| ] |
|
| yellow |
|
| yellow |
|
|- |
|
|- |
| Line 46: |
Line 76: |
|
| red |
|
| red |
|
|- |
|
|- |
|
| <sub>2</sub> |
|
| ]]<sub>2</sub> |
|
| orange |
|
| orange |
|
|- |
|
|- |
| Line 56: |
Line 86: |
|
|- |
|
|- |
|
|} |
|
|} |
|
|
Cp*H is a precursor to ] compounds containing the {{chem|C|5|Me|5|−}} ], commonly called Cp*<sup>−</sup>.<ref>{{cite book |last=Yamamoto |first=A. |title=Organotransition Metal Chemistry: Fundamental Concepts and Applications |date=1986 |page=105 |isbn=9780471891710 |publisher=] |url-access=registration |url=https://archive.org/details/organotransition00yama/page/105}}</ref> |
|
|
|
|
|
Some representative reactions leading to such Cp*-metal complexes follow:<ref>{{cite journal | title = Organometallic chemistry of the transition metals XXI. Some π-pentamethylcyclopentadienyl derivatives of various transition metals | author = R. B. King, M. B. Bisnette | journal = ] | volume = 8 | year = 1967 | pages = 287–297 | doi = 10.1016/S0022-328X(00)91042-8}}</ref> |
|
Some representative reactions leading to such Cp*–metal complexes follow:<ref>{{cite journal | title = Organometallic chemistry of the transition metals XXI. Some π-pentamethylcyclopentadienyl derivatives of various transition metals | first1= R. B. |last1=King|first2= M. B.|last2= Bisnette | journal = ] | volume = 8 | year = 1967 | pages = 287–297 | doi = 10.1016/S0022-328X(00)91042-8 | issue = 2}}</ref> |
|
|
Deprotonation with ]: |
|
:Cp*H + ] → Cp*Li + ] |
|
|
:Cp*Li + ] → Cp*TiCl<sub>3</sub> + ] |
|
:Cp*H + C<sub>4</sub>H<sub>9</sub>Li → Cp*Li + C<sub>4</sub>H<sub>10</sub> |
|
|
Synthesis of (pentamethylcyclopentadienyl)titanium trichloride: |
|
|
:Cp*Li + TiCl<sub>4</sub> → Cp*TiCl<sub>3</sub> + LiCl |
|
|
Synthesis of (pentamethylcyclopentadienyl)iron dicarbonyl dimer from ]: |
|
⚫ |
:2 Cp*H + 2 Fe(CO)<sub>5</sub>]] → <sub>2</sub> + H<sub>2</sub> + 6 CO |
|
⚫ |
This method is analogous to the route to the related Cp complex, see ]. |
|
|
|
|
|
|
Some Cp* complexes are prepared using silyl transfer: |
| ⚫ |
:2 Cp*H + 2 ] → <sub>2</sub> + H<sub>2</sub> |
|
|
|
:Cp*Li + Me<sub>3</sub>SiCl → Cp*SiMe<sub>3</sub> + LiCl |
| ⚫ |
For the related Cp complex, see ]. |
|
|
⚫ |
:Cp*SiMe<sub>3</sub> + TiCl<sub>4</sub> → Cp*TiCl<sub>3</sub> + Me<sub>3</sub>SiCl |
|
|
|
|
|
An instructive but obsolete route to Cp* complexes involves the use of hexamethyl ]. This method was traditionally used for preparation of the chloro-bridged dimers <sub>2</sub>]] and <sub>2</sub>. Such syntheses rely on a ] induced rearrangement of hexamethyl Dewar benzene<ref>{{cite journal |last1= Paquette|first1= L. A.|last2= Krow|first2= G. R.|year= 1968|title= Electrophilic Additions to Hexamethyldewarbenzene|journal= ]|volume= 9|issue= 17|pages= 2139–2142|url= |doi= 10.1016/S0040-4039(00)89761-0}}</ref><ref>{{cite journal |last1= Criegee|first1= R.|last2= Gruner|first2= H.|year= 1968|title= Acid-catalyzed Rearrangements of Hexamethyl-prismane and Hexamethyl-Dewar-benzene|journal= ]|volume= 7|issue= 6|pages= 467–468|url= |doi= 10.1002/anie.196804672}}</ref> to a substituted pentamethylcyclopentadiene prior to reaction with the hydrate of either ]<ref>{{cite journal |last1= Kang|first1= J. W.|last2= Mosley|first2= K.|last3= Maitlis|first3= P. M.|authorlink3=Peter Maitlis|year= 1968|title= Mechanisms of Reactions of Dewar Hexamethylbenzene with Rhodium and Iridium Chlorides|journal= ]|issue= 21|pages= 1304–1305|url= |doi= 10.1039/C19680001304}}</ref> or ].<ref>{{cite journal |last1= Kang|first1= J. W.|last2= Maitlis|first2= P. M.|authorlink2=Peter Maitlis|year= 1968|title= Conversion of Dewar Hexamethylbenzene to Pentamethylcyclopentadienylrhodium(III) Chloride|journal= ]|volume= 90|issue= 12|pages= 3259–3261|url= |doi= 10.1021/ja01014a063}}</ref> |
|
A now-obsolete route to Cp* complexes involves the use of ]. This method was traditionally used for preparation of the chloro-bridged dimers </nowiki><sub>2</sub>]] and </nowiki><sub>2</sub>]], but has been discontinued with the increased commercial availability of Cp*H. Such syntheses rely on a ] induced rearrangement of hexamethyl Dewar benzene<ref>{{cite journal |last1= Paquette|first1= L. A.|last2= Krow|first2= G. R.|year= 1968|title= Electrophilic Additions to Hexamethyldewarbenzene|journal= ]|volume= 9|issue= 17|pages= 2139–2142|doi= 10.1016/S0040-4039(00)89761-0}}</ref><ref>{{cite journal |last1= Criegee|first1= R.|last2= Gruner|first2= H.|year= 1968|title= Acid-catalyzed Rearrangements of Hexamethyl-prismane and Hexamethyl-Dewar-benzene|journal= ]|volume= 7|issue= 6|pages= 467–468|doi= 10.1002/anie.196804672}}</ref> to a substituted pentamethylcyclopentadiene prior to reaction with the hydrate of either ]<ref>{{cite journal |last1= Kang|first1= J. W.|last2= Mosley|first2= K.|last3= Maitlis|first3= P. M.|author-link3=Peter Maitlis|year= 1968|title= Mechanisms of Reactions of Dewar Hexamethylbenzene with Rhodium and Iridium Chlorides|journal= ]|issue= 21|pages= 1304–1305|doi= 10.1039/C19680001304}}</ref> or ].<ref>{{cite journal |last1= Kang|first1= J. W.|last2= Maitlis|first2= P. M.|author-link2=Peter Maitlis|year= 1968|title= Conversion of Dewar Hexamethylbenzene to Pentamethylcyclopentadienylrhodium(III) Chloride|journal= ]|volume= 90|issue= 12|pages= 3259–3261|doi= 10.1021/ja01014a063|bibcode= 1968JAChS..90.3259K}}</ref> |
|
|
|
|
|
<sub>2</sub> using hexamethyl Dewar benzene.]] |
|
:<sub>2</sub> using hexamethyl Dewar benzene]] |
|
|
|
|
|
===Comparison of Cp* with Cp=== |
|
===Comparison to other Cp ligands=== |
|
|
] |
|
Complexes of pentamethylcyclopentadienyl differ in several ways from the more common cyclopentadienyl (Cp) derivatives. Being more electron-rich, Cp* is a stronger donor and is less easily removed from the metal. Consequently its complexes exhibit increased thermal stability. Its steric bulk allows the isolation of complexes with fragile ligands. Its bulk also attenuates intermolecular interactions, decreasing the tendency to form polymeric structures. Its complexes also tend to be highly soluble in non-polar solvents. |
|
|
|
Complexes of pentamethylcyclopentadienyl differ in several ways from the more common cyclopentadienyl (Cp) derivatives. Being more electron-rich, Cp*<sup>−</sup> is a stronger donor and dissociation, like ring-slippage, is more difficult with Cp* than with Cp.<ref>{{Cite journal|last1=Kuwabara|first1=Takuya|last2=Tezuka|first2=Ryogen|last3=Ishikawa|first3=Mikiya|last4=Yamazaki|first4=Takuya|last5=Kodama|first5=Shintaro|last6=Ishii|first6=Youichi|date=2018-06-25|title=Ring Slippage and Dissociation of Pentamethylcyclopentadienyl Ligand in an (η 5 -Cp*)Ir Complex with a κ 3 - O , C , O Tridentate Calixarene Ligand under Mild Conditions|journal=Organometallics|language=en|volume=37|issue=12|pages=1829–1832|doi=10.1021/acs.organomet.8b00257|issn=0276-7333}}</ref> The fluorinated ligand, (trifluoromethyl)tetramethylcyclopentadienyl, C<sub>5</sub>Me<sub>4</sub>CF<sub>3</sub>, combines the properties of Cp and Cp*: it possesses the steric bulk of Cp* but has electronic properties similar to Cp, the electron-donation from the methyl groups being "canceled out" by the electron-accepting nature of the trifluoromethyl substituent.<ref>{{Cite journal|last1=Gassman|first1=Paul G.|last2=Mickelson|first2=John W.|last3=Sowa|first3=John R.|date=1992-08-01|title=1,2,3,4-Tetramethyl-5-(trifluoromethyl)cyclopentadienide: a unique ligand with the steric properties of pentamethylcyclopentadienide and the electronic properties of cyclopentadienide|journal=Journal of the American Chemical Society|volume=114|issue=17|pages=6942–6944|doi=10.1021/ja00043a065|bibcode=1992JAChS.114.6942G |issn=0002-7863}}</ref> Its steric bulk stabilizes complexes with fragile ligands. Its bulk also attenuates intermolecular interactions, decreasing the tendency to form polymeric structures. Its complexes also tend to be more soluble in non-polar solvents. The methyl group in Cp* complexes can undergo ] leading to "]es". ] are known that are far more sterically encumbered than Cp*. |
|
|
|
|
<references/> |
|
|
|
|
|
|
==See also== |
|
==See also== |
|
|
*] |
|
*] |
|
*] |
|
|
|
|
| Line 83: |
Line 120: |
|
Volume 202, Issues 1-3 , 16 October 2000, Pages 19-29--> |
|
Volume 202, Issues 1-3 , 16 October 2000, Pages 19-29--> |
|
|
|
|
|
] |
|
] |
|
] |
|
] |
|
] |
|
|
|
|
|
] |
|
|
] |
|