Sulfonium cations as versatile strongly π-acidic ligands

Ruiping Li,Yuri Tulchinsky,Nitsan Barel,Françoise Tibika,Vasudevan Subramaniyan,Orit Cohen

doi:10.1039/d2sc00588c

Abstract

More than a century old, sulfonium cations are still intriguing species in the landscape of organic chemistry. On one hand they have found broad applications in organic synthesis and materials science, but on the other hand, while isoelectronic to the ubiquitous tertiary phosphine ligands, their own coordination chemistry has been neglected for the last three decades. Here we report the synthesis and full characterization of the first Rh(i) and Pt(ii) complexes of sulfonium. Moreover, for the first time, coordination of an aromatic sulfonium has been established. A thorough computational analysis of the exceptionally short S–Rh bonds obtained attests to the strongly π-accepting nature of sulfonium cations and places them among the best π-acceptor ligands available today. Our calculations also show that embedding within a pincer framework enhances their π-acidity even further. Therefore, in addition to the stability and modularity that these frameworks offer, our pincer complexes might open the way for sulfonium cations to become powerful tools in π-acid catalysis.

Highlights

Rethinking the coordination chemistry of main group elements has o en led to breakthroughs in metal-based homogeneous catalysis
We report the rst synthesis and characterization of a series of complexes of both aliphatic and aromatic sulfonium cations with Rh(I) and Pt(II), two representatives of the Pt metal group,[17] which lies at the core of today's homogeneous catalysis (Chart 1b)
Ligand design and synthesis Obviously, coordination of the sulfonium cation is hindered by an electrostatic repulsion between its positive charge and that of a metal center

Summary

Introduction

Rethinking the coordination chemistry of main group elements has o en led to breakthroughs in metal-based homogeneous catalysis. In both the analogous aliphatic sulfoxide pincer complex 8 that we prepared for comparison (Fig. S17†) and the reported aromatic ones,[24] the Rh–S bonds are still longer than in their sulfonium counterparts (2.135 and 2.134 A, respectively).

Results

Conclusion