Dipotassium cyclooctatetraenide, sometimes abbreviated K₂COT, is an

organopotassium compound Organosodium chemistry is the chemistry of organometallic compounds containing a carbon to sodium chemical bond. The application of organosodium compounds in chemistry is limited in part due to competition from organolithium compounds, which are ...

with the formula K₂C₈H₈. It is a brown solid that is used as a precursor to cyclooctatetraenide complexes, such as

uranocene Uranocene, U(C8H8)2, is an organouranium compound composed of a uranium atom sandwiched between two cyclooctatetraenide rings. It was one of the first organoactinide compounds to be synthesized. It is a green air-sensitive solid that dissolves in ...

(U(C₈H₈)₂). Analogs of K₂C₈H₈ are known with ring substituents, with different alkali metals, and with various complexants.

Preparation and structure

Potassium cyclooctatetraenide is formed by the reaction of

cyclooctatetraene 1,3,5,7-Cyclooctatetraene (COT) is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as nnulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature. Because of ...

with

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...

metal: :2 K + C₈H₈ → K₂C₈H₈ The reaction entails 2-electron reduction of the polyene and is accompanied by a color change from colorless to brown. The structure of K₂(

diglyme Diglyme, or bis(2-methoxyethyl) ether, is a solvent with a high boiling point. It is an organic compound which is the dimethyl ether of diethylene glycol. (The name ''diglyme'' is a portmanteau of ''diglycol methyl ether''.) It is a colorless li ...

)C₈H₈ has been characterized by

X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

of the derivatives with

complexed to the potassium cations. The C₈H₈ unit is planar with an average C-C distance of 1.40 A.{{cite journal , author = J. H. Noordik, T. E. M. van den Hark, J. J. Mooij and A. A. K. Klaassen , title = Dipotassium(I) cyclooctatetraenide-1-methoxy-2-(2-methoxyethoxy)ethane , journal = Acta Crystallogr B , volume = 30 , date = 1974 , issue = 30 , pages = 833–835 , doi = 10.1107/S0567740874003840

References

Potassium compounds Non-benzenoid aromatic carbocycles