2.2.2-Cryptand as a bidentate ligand in rare-earth metal chemistry

Abstract

The 2.2.2-cryptand ligand (crypt) that is heavily used in reductions of rare-earth metal complexes to encapsulate alkali metals has been found to function as a bidentate ligand to rare-earth metal ions in some cases. The X-ray crystal structures of the reduced dinitrogen metal complex, [{(R₂N)₂Ce(crypt-κ²-O,O′)}₂(μ–η²:η²-N₂)] (R = SiMe₃), and the ytterbium metallocene, (C₅Me₅)₂Yb(crypt-κ²-O,O′), are presented to demonstrate this binding mode. The implications of this available binding mode in rare-earth metal cryptand chemistry are discussed.