Controlling Al- Interactions in Group 1 Metal Aluminyls ( = Li, Na, and K). Facile Conversion of Dimers to Monomeric and Separated Ion Pairs.

The aluminyl compounds [{Al(NON)}] (NON = [O(SiMeNDipp)], Dipp = 2,6-PrCH), which exist as contacted dimeric pairs in both the solution and solid states, have been converted to monomeric ion pairs and separated ion pairs for each of the group 1 metals, = Li, Na, and K. The monomeric ion pairs contain discrete, highly polarized Al- bonds between the aluminum and the group 1 metal and have been isolated with monodentate (THF, = Li and Na) or bidentate (TMEDA, = Li, Na, and K) ligands at . The separated ion pairs comprise group 1 cations that are encapsulated by polydentate ligands, rendering the aluminyl anion, [Al(NON)] "naked". For = Li, this structure type was isolated as the [Li(TMEDA)] salt directly from a solution of the corresponding contacted dimeric pair in neat TMEDA, while the polydentate [2.2.2]cryptand ligand was used to generate the separated ion pairs for the heavier group 1 metals = Na and K. This work shows that starting from the corresponding contacted dimeric pairs, the extent of the Al- interaction in these aluminyl systems can be readily controlled with appropriate chelating reagents.