1,5-Cyclooctadiene

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1,5-Cyclooctadiene
Skeletal formula of 1,5-cyclooctadiene
Ball and stick model of 1,5-cyclooctadiene
Names
Systematic IUPAC name
Cycloocta-1,5-diene[1]
Identifiers
111-78-4 YesY
1552-12-1 (Z,Z) YesY
5259-71-2 (Z,E) YesY
17612-50-9 (E,E) YesY
Abbreviations 1,5-COD
2036542

1209288 (Z,Z)
ChemSpider 7843 N
74815 (Z,Z) YesY
18520443 (Z,E) YesY
19971660 (E,E) YesY
EC Number 203-907-1
Jmol 3D model Interactive image
MeSH 1,5-cyclooctadiene
PubChem 8135
82916 (Z,Z)
5364364 (Z,E)
5702534 (E,E)
RTECS number GX9560000

GX9620000 (Z,Z)
UN number 2520
  • InChI=1S/C8H12/c1-2-4-6-8-7-5-3-1/h1-2,7-8H,3-6H2/b2-1-,8-7- YesY
    Key: VYXHVRARDIDEHS-QGTKBVGQSA-N YesY
  • InChI=1/C8H12/c1-2-4-6-8-7-5-3-1/h1-2,7-8H,3-6H2/b2-1-,8-7-
    Key: VYXHVRARDIDEHS-QGTKBVGQBM
  • C1CC=CCCC=C1
Properties
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
1.493
Thermochemistry
198.9 J K−1 mol−1
250.0 J K−1 mol−1
21-27 kJ mol−1
-4.890--4.884 MJ mol−1
Vapor pressure {{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
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. It is a colorless liquid with a strong odor.[2][3] 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:

Synthesis of 9-BBN dimer.png

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

2,6-Dichloro-9-thiabicyclo[3.3.1]nonane, synthesis and reactions

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 binds to low-valent metals via both alkene groups. 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 is a precursor to an 16e complex of ethylene:

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 → Ni(CO)4 + 2 COD

The product Ni(CO)4 is highly toxic, thus it is advantageous to generate it in the reaction vessel upon demand. Other low-valent metal complexes of COD include cyclooctadiene rhodium chloride dimer, cyclooctadiene iridium chloride dimer, and Fe(COD)(CO)3, and Crabtree's catalyst.

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

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  4. ↑ Thomas Schiffer, Georg Oenbrink “Cyclododecatriene, Cyclooctadiene, and 4-Vinylcyclohexene” in Ullmann’s Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.; Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.; Lua error in package.lua at line 80: module 'strict' not found.Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
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