Abstract
Lewis acids and their related weakly coordinating anions (WCAs) are central species in chemistry, and tuning their properties toward different purposes is still a challenging field of research. In this work, the properties of the Lewis acid Al-(OTe(R))(3) have been investigated using the advantages of the OTeF(3)(C(6)F(5))(2) ligand (OTe(R)). Its Lewis acidity was evaluated by means of fluoride ion affinity (FIA) calculations, indicating that it is a Lewis superacid. Complementary analysis using the Gutmann-Beckett method by the synthesis of the Al-(OTe(R))(3)·OPEt(3) adduct rendered similar results, yet for the heavier Ga species this adduct formation was not possible, as only GaEt-(OTe(R))(2)·OPEt(3) was obtained. The reported new Lewis acid was further stabilized as acid-base adducts with tetrahydrofuran and dimethyl carbonate. The isolation of the free Lewis acid proved challenging due to fluoride abstraction from its own ligand, as shown by quantum-chemical calculations. Derived from the Lewis superacid Al-(OTe(R))(3) two weakly coordinating anions, the fluoride adduct [FAl-(OTe(R))(3)](-) and the even less coordinating mixed anion [(F(5)TeO)-Al-(OTe(R))(3)](-), were synthesized. Among them, the synthetically useful silver salt Ag-[(F(5)TeO)-Al-(OTe(R))(3)] stands out, which could be used to generate a strong Brønsted acid by reaction with HCl as well as the [Ph(3)C](+) cation via reaction with Ph(3)CCl. Electrostatic potential surface analysis confirmed the more efficient delocalization of the negative charge and enhanced shielding of oxygen atoms in [(F(5)TeO)-Al-(OTe(R))(3)](-) compared to [FAl-(OTe(R))(3)](-) and [Al-(OTeF(5))(4)](-), and therefore its potential as a promising new WCA.