Organic Chemistry Seminar: Sulfonium-based Ligands for Π-acid Catalysis

Abstract:

In this talk I will a new class of electron-withdrawing ligands based on sulfonium cations. These positively charged species of sulfur are isoelectronic and isolobal to tertiary phosphines. However, unlike the ubiquitous use of the phosphines as supporting ligands in catalysis, coordinative chemistry of sulfonium cations remained nearly unexplored with only a handful of reported examples. We demonstrated that embedding sulfonium cations within a pincer framework allowed the synthesis of the first sulfonium complexes of Rh(I) and Pt(II). Furthermore, our calculations showed that geometric constraints imposed by the pincer scaffold in those complexes enhance the inherent character of sulfonium cation as a strong π-acid.(1)  Moreover, sulfonium pincer ligands with a rigid thioxanthone-based backbone allowed to obtain a unique tris-cationic sulfonium Pt(II) complex, stable enough for isolation, despite the strong electrostatic repulsion within its S+−Pt2+ core. This complex was shown to be a potent π-acid catalyst, constituting the first example of employing a sulfonium cation as an ancillary ligand in homogeneous catalysis.(2)

References:

(1)    Ruiping Li, Yuri Tulchinsky* et al. Chem. Sci., 2022, 13, 4770–4778.

(2)    Ruiping Li, Yuri Tulchinsky* et al. Angew. Chem. Int. Ed., 2024, 136 (2), e202314997.
 

Event Organizer: Dr. Muhammad Jbara