The importance of the electronic and steric features of the ancillary ligands on the rate of cis–trans isomerization of olefins coordinated to palladium(0) centre. A study involving (Z)-1,2-ditosylethene as olefin model

Platinum(0)-η2-1,2-(E)ditosylethene Complexes Bearing Phosphine, Isocyanide and N-Heterocyclic Carbene Ligands: Synthesis and Cytotoxicity towards Ovarian and Breast Cancer Cells

A wide range of platinum(0)-η2-(E)-1,2-ditosylethene complexes bearing isocyanide, phosphine and N-heterocyclic carbene ancillary ligands have been prepared with high yields and selectivity. All the novel products underwent thorough characterization using spectroscopic techniques, including NMR and FT-IR analyses. Additionally, for some compounds, the solid-state structures were elucidated through X-ray diffractometry. The synthesized complexes were successively evaluated for their potential as anticancer agents against two ovarian cancer cell lines (A2780 and A2780cis) and one breast cancer cell line (MDA-MB-231). The majority of the compounds displayed promising cytotoxicity within the micromolar range against A2780 and MDA-MB-231 cells, with IC50 values comparable to or even surpassing those of cisplatin. However, only a subset of compounds was cytotoxic against cisplatin-resistant cancer cells (A2780cis). Furthermore, the assessment of antiproliferative activity on MRC-5 normal cells revealed certain compounds to exhibit in vitro selectivity. Notably, complexes 3d, 6a and 6b showed low cytotoxicity towards normal cells (IC50 > 100 µM) while concurrently displaying potent cytotoxicity against cancer cells.

Chemoselective oxidative addition of vinyl sulfones mediated by palladium complexes bearing picolyl-N-heterocyclic carbene ligands

The manifold interactions of (E)- or (Z)-1,2-ditosylethene with a palladium(0) centre bearing picolyl-NHC carbene ligands have been studied thoroughly. (E)-1,2-Ditosylethene produces the expected and stable η²-olefin palladium complexes, whereas the coordination of the Z derivative alternatively promotes the isomerization of the olefin itself or an oxidative addition process depending on the steric bulkiness of carbene substituents and/or the adopted synthetic procedure. Remarkably, the oxidative addition pathway involves a selective S-vinyl (not S-aryl) breaking and produces selectively the S- rather than O-coordinated sulfinate. A mechanistic study has clarified the reasons of the chemoselectivity of the process, which was proved to be kinetically controlled. All the involved species have been isolated and exhaustively characterized. In particular, we report the first example of the X-ray crystal structure of a complex bearing one vinyl and one S-sulfinate fragment coordinated to palladium.