Thiosaccharinate binding to palladium(II) and platinum(II): Synthesis and molecular structures of sulfur-bound complexes [M(κ1-tsac)2(κ2-diphosphane)]

Palladium(II) and platinum(II) thiosaccharinate complexes [M(κ1-tsac)2{κ2-Ph2P(CH2)nPPh2}] (M = Pd, Pt; n = 1–4) have been prepared, palladium complexes from reaction of [Pd(tsac)2]·H2O with diphosphanes and platinum complexes from addition of thiosaccharin to [PtCl2{κ2-Ph2P(CH2)nPPh2}] in the presence of triethylamine. All complexes have been fully characterized and the crystal structures of [Pd(κ1-tsac)2(κ2-dppp)] (n = 3) and [Pt(κ1-tsac)2(κ2-dppm)] (n = 1) have been determined confirming that thiosaccharinate ligands are S-bound. The larger ring complexes (n = 3, 4) are fluxional in solution being attributed to the conformational flexibility of the diphosphane backbones The bis(diphosphane) complexes, [M(κ1-tsac)2(κ1-dppm)2] (M = Pd, Pt), have also been prepared upon treatment of [Pd(tsac)2]·H2O with two equivalents of dppm or addition of thiosaccharin to [Pt(κ2-dppm)2]Cl2 in the presence of triethylamine in which the diphosphanes bind in a monodentate fashion. Both are highly fluxional in solution, changes in the 31P{1H} NMR spectra as a function of temperature being interpreted as the exchange of bound and unbound phosphorus atoms.

Graphical abstractPalladium(II) and platinum(II) thiosaccharinate complexes M(κ1-tsac)2{κ2-Ph2P(CH2)nPPh2] (M = Pd, Pt; n = 1–4) have been prepared. In all the thiosaccharinate ligands are S-bound as confirmed in the X-ray crystal structures of Pd(κ1-tsac)2(κ2-dppp) and Pt(κ1-tsac)2(κ2-dppm). With excess dppm the bis(diphosphine) complexes, M(κ1-tsac)2(κ1-dppm)2 (M = Pd, Pt) can be prepared. They are supposed to contain both bound and non-bound phosphorus centers but these interconvert rapidly in solution.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► New palladium and platinum thiosaccharinate complexes have been prepared. ► In all the thiosaccharinate ligands bind in a monodentate fashion through sulfur. ► They are fluxional in solution via inversion at sulfur. ► With dppm two bis(diphosphine) complexes have been isolated. ► They are highly fluxional via a process which interconverts bound and free phosphorus atoms.