Reactions of (-)-sparteine with alkali metal HMDS complexes: conventional meets the unconventional.

'Conventional' (-)-sparteine adducts of lithium and sodium 1,1,1,3,3,3-hexamethyldisilazide (HMDS) were prepared and characterised, along with an unexpected and 'unconventional' hydroxyl-incorporated sodium sodiate, [(-)-sparteine x Na(mu-HMDS)Na x (-)-sparteine](+)[Na(4)(mu-HMDS)(4)(OH)](-)--the complex anion of which is the first inverse crown ether anion.