Pentadienyl
In chemistry, pentadienyl refers to the organic radical, anion, or cation with the formula [CH2CHCHCHCH2]z, where z = 0, −1, +1, respectively.
Organometallic chemistry[]
In organometallic chemistry, the pentadienyl anion is a ligand, the acyclic analogue of the more-common cyclopentadienyl anion. The pentadienyl anion is generated by deprotonation of pentadiene. A number of complexes are known, including bis(pentadienyl) iron, Fe(C5H7)2, the "open" analog of ferrocene. Only few pentadienyl complexes feature simple C5H7 ligands. More common is the dimethyl derivative 2,4-Me2C5H5. Additionally, many pentadienyl ligands are cyclic, being derived from the addition of hydride to η6-arene complexes or hydride abstraction from cyclohexadiene complexes.[1][2]
The first pentadienyl complex to be reported was derived from protonolysis of a complex of pentadienol:[3]
- Fe(C5H7OH)(CO)3 + H+ → [Fe(C5H7)(CO)3]+ + H2O
Treatment of this cation with sodium borohydride gives the pentadiene complex:
- [Fe(C5H7)(CO)3]+ + H− → Fe(C5H8)(CO)3
Organic chemistry[]
In organic chemistry, the pentadienyl radical, C
5H•
7, is of some significance as an especially stabilized radical. The radical is delocalized over five carbon centers. Consequently the C−H bond in the diene (CH2(CH=CH2)) is especially weak. Fats derivatives containing this "doubly allylic" group are collectively called drying oils. They tend to polymerize in a useful way upon exposure to air.
Biochemistry[]
Cyclooxygenases ("COX") are enzymes that generate prostanoids, including thromboxane and prostaglandins such as prostacyclin. Aspirin and ibuprofen exert their effects through inhibition of COX.
References[]
- ^ Lothar Stahl, Richard D. Ernst (2007). "Pentadienyl Complexes of the Group 4 Transition Metals". Advances in Organometallic Chemistry. 55: 137–199. doi:10.1016/S0065-3055(07)55003-3.CS1 maint: uses authors parameter (link)
- ^ Richard D. Ernst (1988). "Structural and reactivity patterns in transition-metal-pentadienyl chemistry". Chem. Rev. 88: 1255–1291. doi:10.1021/cr00089a013.
- ^ Mahler, J. E.; Pettit, R. (1962). "Pentadienyl and Hexadienyl Carbonium Ions as Ligands in Stable Complex Cations". J. Am. Chem. Soc. 84: 1511–1512. doi:10.1021/ja00867a051.CS1 maint: uses authors parameter (link)
- Anions
- Free radicals