Platinum metal ditelluroether complexes: synthesis, spectroscopic and structural studies of [M(L–L)2][PF6]2 [M = Pd or Pt, L–L = RTe(CH2)3TeR (R = Me or Ph) or C6H4(TeMe)2-o], [Rh(L–L)2Cl2]PF6, [Ru(L–L)2X2] (X = Cl, Br or I) and [Ru(L–L)2(PPh3)Cl]PF6

Abstract

The reaction of [MCl₂(MeCN)₂] (M = Pd or Pt) with L–L (RTe(CH₂)₃TeR (R = Me or Ph) or C₆H₄(TeMe)₂-o) and TlPF₆ in a 1∶2∶2 ratio in MeCN gave planar [M(L–L)₂][PF₆]₂ which was confirmed by an X-ray crystallographic study of [Pd{meso-C₆H₄(TeMe)₂-o}₂][PF₆]₂. The complexes trans-[Ru(L–L)₂X₂] (X = Cl, Br or I) were prepared from [Ru(dmf)₆][CF₃SO₃]₃, L–L and LiX, whilst [Ru(PPh₃)₃Cl₂], L–L and NH₄PF₆ gave trans-[Ru(L–L)₂(PPh₃)Cl]PF₆. The crystal structure of [Ru{MeTe(CH₂)₃TeMe}₂(PPh₃)Cl][PF₆] revealed one ditelluroether in the meso form and the other in the DL, the first time both stereoisomers have been crystallographically identified in the same compound. In contrast in trans-[Ru{PhTe(CH₂)₃TePh}₂Cl₂] both ditelluroethers are meso forms. For Pd, Pt and Ru multinuclear NMR spectroscopy (¹H, ¹²⁵Te-{¹H}, ¹⁹⁵Pt) showed a mixture of stereoisomeric forms in solution, and for the compounds of Pd and Pt pyramidal inversion at Te is fast on the NMR timescales at ambient temperatures. Reaction of RhCl₃·3H₂O, L–L and NH₄PF₆ gave [Rh(L–L)₂Cl₂]PF₆ which appear to be predominantly trans isomers based upon their NMR and UV/vis spectra. Attempts to oxidise the complexes of Pt^II or Ru^II (to Pt^IV or Ru^III) with halogens or electrochemically were unsuccessful, contrasting with the successful oxidation of analogous complexes with dithioether or diselenoether ligands.