Indyllithium and the Indyl Anion [InL]^- : Heavy Analogues of N-Heterocyclic Carbenes

Reduction of the indate complex In(NON^Ar )(μ-Cl)₂ Li(OEt₂ )₂ (NON^Ar =[O(SiMe₂ NAr)₂ ]^2- ; Ar=2,6-iPr₂ C₆ H₃ ) with sodium generates the In^II diindane species [In(NON^Ar )]₂ . Further reduction with a mixture of potassium and [2.2.2]crypt affords the In^I N-heterocyclic indyl anion [In(NON^Ar )]^- , which crystallizes with a non-contacted [K([2.2.2]crypt)]⁺ cation. The indyl anion can also be isolated as the indyllithium compound In(NON^Ar )(Li{THF}₃ ), which contains an In-Li bond. Density functional theory calculations show that the HOMO of the indyl anion is a metal-centred lone pair, and preliminary reactivity studies confirm its nucleophilic behaviour.