The perfluoroadamantoxy aluminate as an ideal weakly coordinating anion? - synthesis and first applications.

Weakly coordinating anions (WCAs) facilitate the stabilization and isolation of highly reactive and almost "naked" cations. Alkoxyaluminate-based WCAs such as [Al(OC(CF 3 ) 3 ) 4 ] - ([ pf ] - ) are widely used due to their synthetic accessibility and their high stability. However, small cations are still able to coordinate the oxygen atoms of the [ pf ] - anion or even to abstract an alkoxy ligand. The novel WCA [Al(OC 10 F 15 ) 4 ] - ([ pfAd ] - ; OC 10 F 15 = perfluoro-1-adamantoxy) is characterized by a very rigid core framework, thus indicating a higher stability towards fluoride-ion abstraction (DFT calculations) and providing hope to generate less disordered crystal structures. The [ pfAd ] - anion was generated by the reaction of the highly acidic alcohol perfluoro-1-adamantanol C 10 F 15 OH with LiAlH 4 in o -DFB. Li[ pfAd ] could not be synthesized free of impurities (and still contains unreacted alcohol). Yet, starting from contaminated Li[ pfAd ], the very useful pure salts Ag[ pfAd ], [Ph 3 C][ pfAd ] and [H(OEt 2 ) 2 ][ pfAd ] could be synthesized. The salts were characterized by NMR spectroscopy, single-crystal X-ray diffraction and IR spectroscopy. Additionally, [NO][ pfAd ] could be synthesized containing alcohol impurities but nonetheless enabled the synthesis of the salt P 9 + [ pfAd ] - . The synthesis of Tl[ pfAd ] in a mixture of H 2 O/acetone/ o -DFB demonstrated the water stability of the [ pfAd ] - anion.