Mixed phosphathia macrocyclic chemistry: synthesis and characterisation of [M(Ph2[14]ane P2S2)]2+(M = Pd or Pt) and [RhCl2(Ph2[14]ane P2S2)]+(Ph2[14]ane P2S2= 8, 12-diphenyl-1, 5-dithia-8, 12-diphosphacyclotetradecane)

Abstract

The new diphosphadithia macrocycle 8, 12-diphenyl-1, 5-dithia-8, 12-diphosphacyclotetradecane (Ph₂[14] ane P₂S₂) has been prepared and the meso isomer isolated as a white solid. Upon reaction with MCl₂(M = Pd or Pt) in the presence of TIPF₆in refluxing MeCN this isomer gave [M (Ph₂[14]aneP₂S₂)][PF₆]₂. The crystal structure of [Pt(Ph₂[14]aneP₂S₂)][PF₆]₂·MeNO₂shows tetradentate P₂S₂ co-ordination at Pt″ giving a distorted square-planar geometry with Pt–P 2.247(3), 2.252(3)Å and Pt–S 2.343(3), 2.341(4)Å. Phosphorus-31 and ¹⁹⁵Pt NMR spectroscopic data confirm retention of this P₂S₂ co-ordination in solution. Treatment of RhCl₃·3H₂O with Ph₂[14]aneP₂S₂in refluxing aqueous EtOH followed by addition of an excess of NH₄PF₆gave [RhCl₂(Ph₂[14]aneP₂S₂)]PF₆as a yellow solid. The ³¹P NMR spectrum indicates that the complex exists as the trans-dichloro isomer exclusively, and a single-crystal X-ray structure determination confirms this. The crystal structure of [RhCl₂(Ph₂[14]aneP₂S₂)] PF₆shows the macrocyclic donor atoms occupying the four equatorial co-ordination sites around the central Rh^III ion, Rh–P 2.286(1 ), 2.300(1 )Å, Rh–S 2.374(1), 2.377(1)Å, with trans-dichloro ligands, Rh–Cl 2.347(1), 2.354(1)Å, giving a distorted octahedral geometry. Cyclic voltammetry shows that the complexes [M(Ph₂[14]aneP₂S₂)][PF₆]₂(M = Pd or Pt) and trans-[RhCl₂(Ph₂[14]aneP₂S₂)]PF₆each exhibit an irreversible reduction at E_pc values of –1.40, –1.93 and –1.06 V vs.ferrocene–ferrocenium respectively.