Sulfonium Cation in the Service of π-Acid Catalysis

17 July 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Modern organic synthesis has been strongly affected by recent advances in π-acid catalysis. To increase the π-acidity of catalytically active metal centers tunable electron-withdrawing ligands have become intensively sought-after. In this context cationic ligands, while still rare, offer quite an intriguing research ground. Recently, we introduced sulfonium cations into the list of available strongly π-acidic ancillary ligands, by embedding them in a robust pincer-type framework. However, the M-S bond in the so-formed sulfonium complexes was still easy to dissociate, precluding their application as π-acid catalysts. Herein we demonstrate that this obstacle can be overcome by increasing the rigidity of the sulfonium pincer scaffold. This allows the formation of a unique tris-cationic Pt(II) complex which, despite the strong electrostatic repulsion between its two constituents, features a remarkably short S-Pt bond. With its highly electrophilic Pt(II) center coordinated by a labile ligand this complex is ideally suited for π-acid catalysis. Indeed, in representative cycloisomerization reactions, it exhibits an enhanced catalytic activity compared to an analogous complex of a neutral thioether-based pincer ligand. This very first example of employing sulfonium-based ligands in homogeneous catalysis places sulfonium on par with the state-of-the-art ancillary ligands for such reactions.


sulfonium cations
π-acid catalysis
electrophilic catalysis

Supplementary materials

Supplementary Info
Synthetic and computational methods, NMR spectra and XRD parameters.


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.