Dipotassium cyclooctatetraenide, sometimes abbreviated K<sub>2</sub>COT, is an organopotassium compound with the formula K<sub>2</sub>C<sub>8</sub>H<sub>8</sub>. It is a brown solid that is used as a precursor to cyclooctatetraenide complexes, such as uranocene (U(C<sub>8</sub>H<sub>8</sub>)<sub>2</sub>). Analogs of K<sub>2</sub>C<sub>8</sub>H<sub>8</sub> are known with ring substituents, with different alkali metals, and with various complexants.
Potassium cyclooctatetraenide is formed by the reaction of cyclooctatetraene with potassium metal:
The reaction entails 2-electron reduction of the polyene and is accompanied by a color change from colorless to brown.
The structure of K<sub>2</sub>(diglyme)C<sub>8</sub>H<sub>8</sub> has been characterized by X-ray crystallography of the derivatives with diglyme complexed to the potassium cations. The C<sub>8</sub>H<sub>8</sub> unit is planar with an average C-C distance of 1.40 A.