Landmark crystal structure of an experimentally utilized tetralithium-tetrapotassium amide-alkoxide superbase

It has long been known that mixtures of organolithium derivatives (e.g., alkyls, amides, or enolates) and heavier alkali metal alkoxides (e.g. tert-butoxides or tert-pentoxides) can exhibit special proton-abstracting powers well beyond the capability of the lithium compounds on their own.[1] A forest of literature has grown around this superbasicity focussing mainly on its exploitation in organic synthesis[2] and, to a lesser extent in polymerization.[3] Yet for all this accumulated knowledge, there is still much uncertainty about the precise identities and structures of these superbasic reagents, which seems remarkable given that in general their two separate components (e.g. nBuLi[4] and tBuOK[5]) have themselves been fully characterized both in solution and in the solid state