1,5-cyclooctadiene
Encyclopedia : 1 : 15 : 15C : 1,5-cyclooctadiene
| 1,5-Cyclooctadiene | |
|---|---|
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| General | |
| Molecular formula | C8H12 |
| Molar mass | 108.18 g/mol |
| Appearance | clear colorless liquid |
| CAS number | [111-78-4] |
| Properties | |
| Density and phase | 0.88 g/ml, liquid |
| Solubility in water | 780 g/mL at 20 °C |
| Melting point | -69.5 °C |
| Boiling point | 151 °C |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) [Chemical infoboxInfobox disclaimer and references] | |
1,5-Cyclooctadiene, commonly abbreviated COD, is a compound with the chemical formula C8H12. It is an important ligand in organometallic chemistry Buehler, C; Pearson, D. Survey of Organic Syntheses. Wiley-Intersciene, New York. 1970. Shriver, D; Atkins, P. Inorganic Chemistry. W. H. Freeman and Co., New York. 1999. Crascall, L; Spencer, J., "Bis(1,5-Cyclooctadiene) Platinum(0)", Inorganic Syntheses (28) 1990 Schumn, R; Ittel, S., "Bis(1,5-Cyclooctadiene) Nickel(0)", Inorganic Syntheses (28) 1990 .
Synthesis
1,5-Cyclooctadiene can be prepared by dimerization of 1-butene in the presence of a nickel catalyst to give 1,5-cyclooctadiene.Reactions
1,5-COD binds to metals in as an η4 ligand, meaning it is attached to the metal center via four atoms. Complexes of the form M(cod)2 are often used as starting materials, where M is Ni, Pd, or Pt. These complexes are attractive because they are sufficiently stable to be isolated but the COD ligands are easily displaced by other ligands. These complexes are more stable than related ethylene complexes M(H2CCH2)4. Part of the stability of cod complexes is attributable to the small entropy change upon dissociation, i.e. a chelate effect. Reactions leading to displacement of cod work best when the complex is added slowly to a solution of displacing ligands. The Pt complex (shown below) is more stable thermodynamically and oxidatively than its Ni analogue.
M(COD)2 synthesis
The common starting material Ni(COD)2 is prepared by reduction of, [Ni(C5H7O2)2]3
- 1/3 [Ni(C5H7O2)2]3 + 2 COD + 2 Al(C2H5)3 → Ni(COD)2 + 2 Al(C2H5)2(C5H7O2) + C2H4 + C2H6
- 2 Li + C8H8 → Li2C8H8
- Li2C8H8 + PtCl2(COD) + 3 C7H10 → [Pt(C7H10)3] + 2 LiCl + C8H8 + C8H12
- Pt(C7H10)3 + 2 COD → Pt(COD)2 + 3 C7H10
Uses of M(COD)2
The platinum complex has been used in many syntheses:
- Pt(COD)2 + 3 C2H4 → Pt(C2H4)3 + 2 COD
- Ni(cod)2 + 4 CO(g) [\overrightarrow] Ni(CO)4 + 2 COD
Extensive work has been reported on complexes of COD, much of which can has been described in Inorganic Syntheses volumes 25, 26 and 28.
Other reactions
COD reacts with borane to 9-Borabicyclo[3.3.1]nonane which is an important reagent in organic chemistry for hydroborations.COD forms in a two-step reaction with first disulfur dichloride and then sulfuryl chloride the compound 2,6-Dichloro-9-thiabicyclo[3.3.1]nonane ''2,6-Dichloro-9-thiabicyclo[3.3.1]nonane: Multigram Display of Azide and Cyanide Components on a Versatile Scaffold'' Molecules 2006, 11, 212-218 [Online article] which can be further modified as the di-azide or di-cyano derivative in a nucleophilic substitution aided by anchimeric assistance.
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