Synthesis, structures and redox properties of platinum metal phosphathia complexes: crystal structures of cis-[RuCl2(RSC2H4SR)]·0.75Et2O and cis-[RhCl2(RSC2H4RS)]PF6·CH2Cl2(R = Ph2PCH2CH2)

Abstract

Reaction of[RuCl₂(py)₄](py = pyridine) with 1 molar equivalent of the new tetradentate acyclic phosphathia compound RSC₂H₄SR (Ph₂PCH₂CH₂SCH₂CH₂SCH₂CH₂PPh₂) or the macrocycle meso-Ph₂[14]aneP₂S₂(4,8-diphenyl-1,11-dithia-4.18-diphosphacyclotetradecane) in refluxing toluene under a nitrogen atmosphere afforded the ruthenium(II) complexes [RuCl₂(RSC₂H₄SR)] and [RuCl₂(Ph₂[14]aneP₂S₂)] respectively as as yellow solids. The crystal structure of [RuCl₂(RSC₂H₄SR)]·0.75Et₂O shows RSC₂H₄SR co-ordinated via all four donor atoms with the two P-donors occupying mutually trans co-ordination sites at Ru^II, and cis-dichlorides completing the overall octahedral stereochemistry, Ru–S 2.294(1), 2.292(1), Ru–P 2.339(2), 2.335(2), Ru–Cl 2.463(1), 2.463(1)Å. Phosphorus-31 NMR spectroscopic studies on the macrocyclic species [RuCl₂(Ph₂[14]aneP₂S₂)] are consistent with a cis-dichloro isomer in which one Cl is trans to P and the other trans to S. Cyclic voltammetry showed a reversible one-electron oxidation occurring at E_½=+0.16 and +0.32 V vs. ferrocene–ferrocenium for [RuCl₂(RSC₂H₄SR)] and [RuCl₂(Ph₂[14]aneP₂S₂)] respectively. The complexes [MCl₂(RSC₂H₄SR)]PF₆(M = Rh or Ir) have also been prepared. The structure of [RhCl₂(RSC₂H₄SR)]PF₆·CH₂Cl₂ shows discrete [RhCl₂(RSC₂H₄SR)]⁺ cations adopting a very similar arrangement to that in the ruthenium(II) analogue, with Rh–P 2.352(2), 2.342(2), Rh–S 2.303(2), 2.297(2), Rh–Cl 2.370(2), 2.359(2)Å. Rhodium-103 NMR spectroscopy reveals a triplet at δ+ 1405 (J_RhP 85 Hz).