A Highly Sterically Encumbered Boron Lewis Acid Enabled by an Organotellurium-Based Ligand.

Lewis acidic boron compounds are ubiquitous in chemistry due to their numerous applications, yet tuning and optimizing their properties towards different purposes is still a challenging field of research. In this work, the boron-based Lewis acid B[OTeF(CF)] was synthesized by reaction of the teflate derivative HOTeF(CF) with BCl or BCl ⋅ SMe. This new compound presents a remarkably high thermal stability up to 300 °C, as well as one of the most sterically encumbered boron centres known in the literature. Theoretical and experimental methods revealed that B[OTeF(CF)] exhibits a comparable Lewis acidity to that of the well-known B(CF). The affinity of B[OTeF(CF)] towards pyridine was accessed by Isothermal Titration Calorimetry (ITC) and compared to that of B(OTeF) and B(CF). The ligand-transfer reactivity of this new boron compound towards different fluorides was demonstrated by the formation of an anionic Au(III) complex and a hypervalent iodine(III) species.