1,5-Cyclooctadiene

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1,5-Cyclooctadiene
Systematic name

Cycloocta-1,5-diene[1]

Identifiers
Abbreviations 1,5-COD
CAS number 111-78-4 YesY, 1552-12-1 (Z,Z), 5259-71-2 (Z,E), 17612-50-9 (E,E)
PubChem 8135, 82916 (Z,Z), 5364364 (Z,E), 5702534 (E,E)
ChemSpider 7843 N, 74815 (Z,Z) YesY, 18520443 (Z,E) YesY, 19971660 (E,E) YesY
EC number 203-907-1
UN number 2520
MeSH 1,5-cyclooctadiene
RTECS number GX9560000

GX9620000 (Z,Z)

Beilstein Reference 2036542

1209288 (Z,Z)

Jmol-3D images Image 1
Properties
Molecular formula C8H12
Molar mass 108.18 g mol−1
Appearance Colorless liquid
Density 0.882 g/mL
Melting point −69 °C; −92 °F; 204 K
Boiling point 150 °C; 302 °F; 423 K
Vapor pressure 910 Pa
Refractive index (nD) 1.493
Thermochemistry
Std enthalpy of
formation ΔfHo298		 21-27 kJ mol-1
Std enthalpy of
combustion ΔcHo298		 -4.890--4.884 MJ mol-1
Standard molar
entropy So298		 250.0 J K-1 mol-1
Specific heat capacity, C 198.9 J K-1 mol-1
Hazards
GHS pictograms
GHS signal word DANGER
GHS hazard statements H226, H304, H315, H317, H319, H334
GHS precautionary statements P261, P280, P301+310, P305+351+338, P331, P342+311
EU classification Xn
R-phrases R10, R36/38, R42/43, R65
S-phrases S23, S26, S36/37, S62
Flash point 32–38 °C
Autoignition temperature 222 °C; 432 °F; 495 K
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

1,5-Cyclooctadiene is the organic compound with the chemical formula C8H12. Generally abbreviated COD, this diene is a useful precursor to other organic compounds and serves as a ligand in organometallic chemistry.[2][3]

Synthesis

1,5-Cyclooctadiene can be prepared by dimerization of butadiene in the presence of a nickel catalyst, a coproduct being vinylcyclohexene. Approximately 10,000 tons were produced in 2005.[4]

Organic reactions

COD reacts with borane to give 9-borabicyclo[3.3.1]nonane,[5] commonly known as 9-BBN, a reagent in organic chemistry used in hydroborations:

COD adds SCl2 (or similar reagents) to give 2,6-dichloro-9-thiabicyclo[3.3.1]nonane:[6]

The resulting dichloride can be further modified as the di-azide or di-cyano derivative in a nucleophilic substitution aided by anchimeric assistance.

Metal complexes

Structure of M(COD)2 for M = Ni, Pd, Pt.

1,5-COD typically binds to low-valent metals via both alkene groups. The complex Ni(COD)2 is a precursor to several nickel(0) and Ni(II) complexes. Metal-COD complexes are attractive because they are sufficiently stable to be isolated, often being more robust than related ethylene complexes. The stability of COD complexes is attributable to the chelate effect. The COD ligands are easily displaced by other ligands, such as phosphines.

Ni(COD)2 is prepared by reduction of anhydrous nickel acetylacetonate in the presence of the ligand, using triethylaluminium [7]

1/3 [Ni(C5H7O2)2]3 + 2 COD + 2 Al(C2H5)3 → Ni(COD)2 + 2 Al(C2H5)2(C5H7O2) + C2H4 + C2H6

The related Pt(COD)2 is prepared by a more circuitous route involving the dilithium cyclooctatetraene:[8]

Li2C8H8 + PtCl2(COD) + 3 C7H10 → [Pt(C7H10)3] + 2 LiCl + C8H8 + C8H12
Pt(C7H10)3 + 2 COD → Pt(COD)2 + 3 C7H10

Extensive work has been reported on complexes of COD, much of which can has been described in volumes 25, 26, and 28 of Inorganic Syntheses. The platinum complex has been used in many syntheses:

Pt(COD)2 + 3 C2H4 → Pt(C2H4)3 + 2 COD

COD complexes are useful as starting materials, one noteworthy example is the reaction:

Ni(COD)2 + 4 CO(g) \rightleftharpoons Ni(CO)4 + 2 COD

The product Ni(CO)4 is highly toxic, thus it is advantageous to generate it in the reaction vessel as opposed to being dispensed directly. Other low-valent metal complexes of COD include Mo(COD)(CO)4, [RuCl2(COD)]n, and Fe(COD)(CO)3. COD is an especially important in the coordination chemistry of rhodium(I) and iridium(I), examples being Crabtree's catalyst and cyclooctadiene rhodium chloride dimer.

The M(cod)2 complexes with nickel, palladium, and platinum have tetrahedral geometry, whereas [M(COD)2]+ complexes of rhodium and iridium are square planar.

(E,E)-COD

E,E-COD synthesis (Stöckmann et al. 2011)

The highly strained trans-trans isomer of 1,5-cyclooctadiene is a known compound. (E,E)-COD was first synthesized by Whitesides and Cope in 1969 by photoisomerization of the cis compound.[9] Another synthesis (double elimination reaction from a cyclooctane ring) was reported by Huisgen in 1987.[10] The molecular conformation of (E,E)-COD is twisted rather than chair-like. The compound has been investigated as a click chemistry mediator.[11]

References

  1. ↑ "AC1L1QCE - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification and Related Records. Retrieved 14 October 2011. 
  2. ↑ Buehler, C; Pearson, D. (1970). Survey of Organic Syntheses. New York: Wiley-Intersciene. 
  3. ↑ Shriver, D; Atkins, P. (1999). Inorganic Chemistry. New York: W. H. Freeman and Co. 
  4. ↑ Thomas Schiffer, Georg Oenbrink “Cyclododecatriene, Cyclooctadiene, and 4-Vinylcyclohexene” in Ullmann’s Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim.
  5. ↑ John A. Soderquist and Alvin Negron (1998), "9-Borabicyclo[3.3.1]nonane Dimer", Org. Synth. ; Coll. Vol. 9: 95 
  6. ↑ Roger Bishop, "9-Thiabicyclo[3.3.1]nonane-2,6-dione", Org. Synth. ; Coll. Vol. 9: 692 Díaz, David Díaz; Converso, Antonella; Sharpless, K. Barry; Finn, M. G. (2006). "2,6-Dichloro-9-thiabicyclo[3.3.1]nonane: Multigram Display of Azide and Cyanide Components on a Versatile Scaffold". Molecules 11 (4): 212–218. doi:10.3390/11040212. 
  7. ↑ Schunn, R; Ittel, S. (1990). "Bis(1,5-Cyclooctadiene) Nickel(0)". Inorg. Synth. Inorganic Syntheses 28: 94. doi:10.1002/9780470132593.ch25. ISBN 978-0-470-13259-3. 
  8. ↑ Crascall, L; Spencer, J. (1990). "Olefin Complexes of Platinum". Inorg. Synth. Inorganic Syntheses 28: 126. doi:10.1002/9780470132593.ch34. ISBN 978-0-470-13259-3. 
  9. ↑ George M. Whitesides; Gerald L. Goe; Arthur C. Cope (1969). "Irradiation of cis,cis-1,5-cyclooctadiene in the presence of copper(I) chloride". J. Am. Chem. Soc. 91 (10): 2608–2616. doi:10.1021/ja01038a036. 
  10. ↑ Dieter Boeckh; Rolf Huisgen; Heinrich Noeth (1987). "Preparation and conformation of (E,E)-1,5-cyclooctadiene". J. Am. Chem. Soc. 109 (4): 1248–1249. doi:10.1021/ja00238a046. 
  11. ↑ Henning Stöckmann; André A. Neves; Henry A. Day; Shaun Stairs; Kevin M. Brindle; Finian J. Leeper (2011). "(E,E)-1,5-Cyclooctadiene: a small and fast click-chemistry multitalent". Chem. Commun. doi:10.1039/C1CC12161H. 
Alkenes
Dienes
Trienes
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