[2.2.2]Cryptand is the organic compound with the formula N(CH<sub>2</sub>CH<sub>2</sub>OCH<sub>2</sub>CH<sub>2</sub>OCH<sub>2</sub>CH<sub>2</sub>)<sub>3</sub>N. This bicyclic molecule is the most studied member of the cryptand family of chelating agents. It is a white solid. Many analogous compounds are known. Their high affinity for alkali metal cations illustrates the advantages of "preorganization", a concept within the area of supramolecular chemistry.
For the design and synthesis of [2.2.2]cryptand, Jean-Marie Lehn shared the Nobel Prize in Chemistry. The compound was originally prepared starting with the diacylation of the diamine-diether:
The resulting macrocyclic diamide is reduced by lithium aluminium hydride. The resulting macrocyclic diamine tetraether reacts with a second equivalent of [CH<sub>2</sub>OCH<sub>2</sub>COCl]<sub>2</sub> to produce the macrobicyclic diamide. This di(tertiary)amide is reduced to the diamine by diborane.
[2.2.2]Cryptand binds K<sup>+</sup> as an octadentate N<sub>2</sub>O<sub>6</sub> ligand. The resulting cation K([2.2.2]cryptand)<sup>+</sup> is lipophilic.