Homoleptic hexathia complexes of rhodium. The synthesis, electrochemistry, and single-crystal X-ray structure of [RhL2][PF6]3(L = 1,4,7-trithiacyclononane)

Abstract

Reaction of [Rh(H₂O)₆]³⁺ with 2 molar equivalents of 1,4,7-trithiacyclononane (L) gives the complex cation [RhL₂]³⁺. The single-crystal X-ray structure of [RhL₂][PF₆]₃ shows a centrosymmetric complex around octahedral Rh^III with Rh–S 2.332(2)Å. The crystals are monoclinic, space group I2/m(alternative setting of C2/m, no. 12), with a= 11.329(3), b= 9.692(3), c= 14.909(4)Å, β= 101.77(2)°, and Z= 2. Cyclic voltammetry of [RhL₂][PF₆]₃ in MeCN (0.1 mol dm^–3 NBuⁿ₄PF₆) at 20°C at platinum electrodes shows two chemically reversible reductions at ¹E_½=–0.71 V, ΔE_p= 71 mV and ²E_½=–1.08 V, ΔE_p= 127 mV vs. ferrocene–ferrocenium, which are assigned to Rh^III–Rh^II and Rh^II–Rh^I redox couples respectively.