$Ortho$-(methylsulfanyl)phenylphosphonates and derivatives: Synthesis and applications as mono- or bidentate ligands for the preparation of platinum complexes

International audienceThe preparation of six phenylphosphonates (and phosphonic acid derivatives) bearing a sulfur group in $ortho$ position was accomplished $via$ either a [1,3]- or a [1,4]-sigmatropic rearrangement. Their complexation with different platinum sources has been studied and the new platinum complexes obtained were characterized by NMR spectroscopy ($^1$H, $^{13}$C, $^{31}$P and $^{195}$Pt). Three runs of experiments were performed. The first was the reaction of ligands 1 and 2 bearing one sulfide and a phosphonate diester functions with potassium tetrachloroplatinate. In the obtained complexes, two molecules of ligand chelate the metal only by the sulfur atom. We were able to observe by $^{195}$Pt and $^{31}$P NMR spectroscopy the $trans$ to $cis$ rearrangement of a dichloro-methyl-($o$-phosphorylbenzyl)sulfide platinum(II) complex upon time, leading to two new species, which are diastereomers of the cis-complex. The second set of experiments involved ligands 1, 2 and 3 bearing one sulfide or sulfoxide and a phosphonate diester moieties, cisplatin and one equivalent of silver nitrate. In the resulting complexes the platinum is coordinated by the sulfur atom of one molecule of ligand. In the third run, the reaction between ligands 4, 5, and 6 bearing one sulfide or sulfoxide and one phosphonic acid or one phosphonic monoester group and the cisplatin diaqua form led to O,S$-$Pt chelates