Mixing Li and Cs in the reduction of corannulene for the assembly of a cesium-capped sandwich with a hexanuclear heterometallic core.

The use of two alkali metals having the greatest ion size mismatch, Li and Cs, in the reduction of bowl-shaped corannulene (CH, 1), results in the preparation of a heterobimetallic organometallic self-assembly, [Cs(diglyme)]//[LiCs(CH)(diglyme)] (2). The X-ray crystallographic investigation of 2 revealed the formation of a triple-decker sandwich having a highly-charged hexanuclear core, (LiCs), held between two tetrareduced corannulene decks. The sandwich is capped by external cesium ions filling the concave cavities of corannulene bowls. The average depth of two CH anions of 0.754(14) Å is significantly greater in 2 compared to the values of 0.241(2)-0.355(2) Å observed in the homometallic lithium sandwiches formed by tetrareduced corannulene, thus illustrating the unique flexibility of its carbon framework to adapt to different internal and external coordination environments.