Friederike Oesten

The properties of the strong Lewis acid Ge(OTeF5)4 are investigated experimentally and quantum-chemically and compared to other germanes with electron-withdrawing ligands. It readily forms the octahedral germanate [NEt4]2[Ge(OTeF5)6] upon reaction with two equivalents of [NEt4][OTeF5]. Additionally, germanes with the formula RxGe(OTeF5)4–x with R = Me, Ph and x = 3, 2, 1 have been characterized. Ph3GeOTeF5 was utilized to generate the germylium ion [GePh3][Al(OTeF5)4] by –OTeF5 abstraction with one of the strongest Lewis acids available─Al(OTeF5)3.

In this work, we present the characterization of Si(OTeF ₅ ) ₄ and its utilization as a Lewis acid. Therefore, the adduct formation toward Si(OTeF ₅ ) ₄ L ₂ (L = 4‐(dimethylamino)pyridine)), Si(OTeF ₅ ) ₄ L (L = 2,2’‐bipyridine, 1,10‐phenanthroline) and [NEt ₄ ] ₂ [Si(OTeF ₅ ) ₆ ] was studied. Furthermore, we compare its Lewis acidity to that of other homoleptic silanes with electron‐withdrawing ligands.

The preparation and characterization of R _x R′ _y SiOTeF ₅ (R = Me, Et, ⁱ Pr, Ph; x = 3, y = 0; R = Pr, ^t Bu, R′ = Me; x = 1, y = 2; 1a‐1f), R ₂ Si(OTeF ₅ ) ₂ (R = Me, Et, ⁱ Pr, Ph; 2a‐2d) and RSi(OTeF ₅ ) ₃ (R = Me, Et, ^t Bu, Ph; 3a‐3d) by reaction of the corresponding chlorosilane and an OTeF ₅ transfer reagent is presented. Molecular structures in the solid state were obtained for Ph ₃ SiOTeF ₅ (1f), Ph ₂ Si(OTeF ₅ ) ₂ (2d) and ^t BuSi(OTeF ₅ ) ₃ (3c). Furthermore, the Lewis acidity was assessed by calculating the fluoride ion affinity (FIA), leading to the observation that a higher number of pentafluoroorthotellurate groups results in an increased FIA.

The synthesis and characterisation of ACF-Si-teflate (teflate: pentafluoroorthotellurate) is reported, which is a solid super Lewis acid generated by incorporating teflate-functionalised silicon containin entities into an aluminium chlorofluoride (ACF) matrix....

This Review surveys the properties and applications of the pentafluoroorthotellurate ("teflate", OTeF₅) ligand and highlights the syntheses of the known teflate-based compounds across the periodic table. Due to the accessibility to several useful teflate transfer reagents and its unique properties, including strong electron-withdrawing character, considerable steric bulk, and stability against oxidation, a variety of intriguing p-block and d-block species have been reported. These encompass highly reactive Lewis acids, versatile weakly coordinating anions, neutral and cationic noble gas compounds, and a wide number of transition metal complexes. The lower analogues of the pentafluoroorthochalcogenate group, OSeF₅ and OSF₅, are described as well, although fewer examples are known. Recent progress in the derivatization of the OTeF₅ group to cis- and trans-PhTeF₄O or trans-(C₆F₅)₂TeF₃O moieties is also discussed, opening pathways to exciting new research directions.