A Rare Example of a Gallium-based Lewis Superacid: Synthesis and Reactivity of Ga(OTeF5)3

Abstract

The Lewis superacid Ga(OTeF5)3 has been synthesized and characterized, revealing a monomeric structure in solution and a dimeric structure in the solid state. Isolated adducts of Ga(OTeF5)3 with strong and weak Lewis bases have been characterized spectroscopically as well as single-crystal X-ray diffractometry. The Lewis acidity of this new species has been evaluated by means of different experimental and theoretical methods, which has allowed to classify it as one of only a few examples of a gallium-based Lewis superacid. The high Lewis acidity of Ga(OTeF5)3 was used to amplify the strength of the Brønsted acid HOTeF5, leading to the protonation of diethyl ether. Furthermore, Ga(OTeF5)3 was utilized to access the strong oxidizing system Ga(OTeF5)3/Xe(OTeF5)2 in SO2ClF, which was successfully employed in the synthesis of the dimethyl chloronium salt [Cl(CH3)2][Ga(OTeF5)4], a strong electrophilic methylation reagent.