Methylcyclopentadiene

Methylcyclopentadiene
Identifiers
PubChem	66775
ChemSpider	60141 Y
Jmol-3D images	Image 1
SMILES C\1=C\C=C(\C)C/1
InChI InChI=1S/C6H8/c1-6-4-2-3-5-6/h2-4H,5H2,1H3 Y Key: NFWSQSCIDYBUOU-UHFFFAOYSA-N Y InChI=1/C6H8/c1-6-4-2-3-5-6/h2-4H,5H2,1H3 Key: NFWSQSCIDYBUOU-UHFFFAOYAV
Properties
Molecular formula	C6H8
Molar mass	80.13 g mol−1
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Methylcyclopentadiene describes three isomeric cyclic diolefins with the formula C₅MeH₅ (Me = CH₃). These isomers are the organic precursor to the methylcyclopentadienyl-ligand (C₅H₄Me, often denoted as Cp'), commonly found in organometallic chemistry. C₅MeH₅ is prepared by thermal cracking its Diels-Alder dimer, followed by distillation to remove cyclopentadiene C₅H₆, a common impurity.^[1]

Relative to the corresponding Cp complexes, complexes of Cp' exhibit enhanced solubility in organic solvents. Furthermore Cp' is often employed to probe the structure of organometallic complexes. For example, (MeC₅H₄)Fe(PPh₃)(CO)I, exhibits four MeC₅H₄ resonances in its ¹H NMR spectrum and five MeC₅H₄ resonances in the ¹³C NMR spectrum. Free rotation of the Cp' ligand does not equivalence the diastereopic protons and carbon centers. The achiral precursor complex (MeC₅H₄)Fe(CO)₂)I exhibits only two MeC₅H₄ resonances in the ¹H NMR spectrum and three MeC₅H₄ resonances in the ¹³C NMR spectrum.^[2]

Structure of (MeC₅H₄)Fe(PPh₃)(CO)I, with labels for the four diastereotopic ring protons.

References

1. ^ Darkwa, James; Giolando, Dean M.; Murphy, Catherine Jones; Rauchfuss, Thomas B.; Müller, A. (1990). "Bis(η5-Methylcyclopentadienyl)Titanium Pentasulfide, Bis(μ-Methylcyclopentadienyl)-Divanadium Pentasulfide, and Bis(μ5-Methylcyclopentadienyl)Divanadium Tetrasulfide". Inorg. Synth. 27: 51. doi:10.1002/9780470132586.ch10. 
2. ^ Carlton, L.; Johnston, P.; Coville, N. J. (1988). "Substituted cyclopentadienyl complexes. II. Carbon-13 NMR spectra of some [(η⁵-C₅H₄Me)Fe(CO)(L)I] complexes". Journal of Organometallic Chemistry 339 (3): 339–43. doi:10.1016/S0022-328X(00)99395-1. 

See also

• Cyclopentadiene
• Pentamethylcyclopentadiene