Homoleptic Cuprates(II) with Multiply Deprotonated α‐Cyclodextrin Ligands

In the presence of cupric ions, α‐cyclodextrin (α‐CD) is multiply deprotonated in alkaline aqueous solution. With lithium or sodium as the counterions, trinuclear sandwich‐type cuprate ions of the formula [Cu 3 (α‐CDH _6 ) 2 ] 6‐ are formed ( 1 and 2 ), whereas dinuclear [Cu 2 (α‐CDH _4 ) 2 ] 4‐ ions are isolated in the form of the potassium ( 3a ) and the rubidium salts ( 3b ). The structures of the cyclodextrinatocuprate ions resemble cylinders, since the usual conical shape of a cyclodextrin is altered due to the formation of shorter hydrogen bonds on the O2/O3 rim of the α‐cyclodextrin torus. Despite anion formation, the cavity of the cyclodextrin is still hydrophobic, giving rise to the intercalation of acetone guests in 2 and 3 .