Co-ordination chemistry of higher oxidation states. Part 41. Synthesis, spectroscopic and electrochemical studies of cationic ruthenium(III) Group 15 and 16 donor ligand complexes. Structure of trans-[Ru{C6F4(AsMe2)2-o}2Br2]BF4

Abstract

The complexes trans-[Ru(L–L)₂X₂]BF₄[X = Cl or Br; L–L = bidentate ligand including C₆H₄(PMe₂)₂-o, C₆H₄(AsMe₂)₂-o, C₆F₄(AsMe₂)₂-o, Me₂PCH₂CH₂PMe₂, Ph₂PCH₂CH₂PPh₂, Ph₂AsCHCHAsPh₂, C₆H₄(PPh₂)₂-o, C₆F₄(PPh₂)₂-o, MeSCH₂CH₂SMe, PhSCH₂CH₂SPh and PhSeCH₂CH₂SePh] have been prepared by nitric acid oxidation of the corresponding [Ru(L–L)₂X₂] in aqueous HBF₄ and in other ways. The complexes have been characterised by analysis, IR and UV/VIS spectroscopies, and magnetic measurements, and the Ru^II–Ru^III redox potentials established by cyclic voltammetry. The crystal structure of trans-[Ru{C₆F₄(AsMe₂)₂-o}₂Br₂]BF₄ has been determined; monoclinic, space group C2/c, a= 22.080(5), b= 18.064(2), c= 8.576(3)Å, β= 96.27(3)°, R= 0.040 for 2266 reflections [F > 3σ(F)]; Ru–Br 2.455(1), Ru–As 2.457(1), 2.460(1)Å. Electrochemical studies have provided evidence for the formation of ruthenium(IV) analogues in solution at low temperatures for certain ligands, but these are too unstable to isolate by chemical means. Comparisons with the analogous iron and osmium systems are made.