Synthesis and dynamic stereochemistry of the complexes [Pt{CH3C(CH2PPh2)3}(SR)(H)](R = H or Ph)

Abstract

The cis square-planar hydrido mercapto derivatives [Pt(triphos)(SH)(H)] and [Pt(triphos)(SPh)(H)][triphos = CH₃C(CH₂PPh₂)₃] have been prepared by reaction of [Pt(triphos)(PPh₃)] with H₂S or HSPh. Analysis of the ¹H and ³¹P NMR data for the two complexes over a temperature range encompassing slow- and fast-exchange limits characterizes these molecules as stereochemically non-rigid on the NMR time-scale. The fluxional behaviour can be explained on the basis of intramolecular exchange of the unco-ordinated phosphorus atom of triphos with the phosphorus atom co-ordinated in cis position to the hydride ligand. At higher temperature, a complete scrambling of the three phosphorus atoms occurs, and at the fast-exchange limit the spin correlation between the phosphorus atoms and platinum metal is retained. The related complexes [Pt(dppp)(SH)(H)](dppp = Ph₂PCH₂CH₂CH₂PPh₂), [Pt(triphos)Cl₂] and [Pt(triphos)(SH)₂] have been prepared in order to clarify the mechanism of the fluxionality for [Pt(triphos)(SR)(H)](R = H or Ph).