Spectroscopic and electrical properties of [Fe(C3X5)2]–(X = S or Se) complexes and crystal structures of [NBun4][Fe(C3S5)2] and [Fe(C5Me5)2][Fe(C3S5)2]

Abstract

Complexes containing the [Fe(C₃S₅)₂]^– anion [C₃S₅^2–= 4,5-dimercapto-1,3-dithiole-2-thionate(2–)] and [Fe(C₃Se₅)₂]^–[C₃Se₅^2–= 4,5-di(hydroseleno)-1,3-diselenole-2-selonate(2–)] have been prepared. Single-crystal X-ray analyses of the [NBuⁿ₄]⁺ and [Fe(C₅Me₅)₂]⁺ salts of [Fe(C₃Se₅)₂]^– revealed dimerized geometries for the anions with square-pyramidal co-ordination around each Fe^III through intermolecular Fe–S linkages. One-dimensional arrays of the dimerized anion moieties are built up via weak sulfur–sulfur non-bonded contacts in the crystal phases. The crystals of both complexes are triclinic, space group P, with cell parameters a= 11.969(3), b= 14.249(3), c= 9.965(2)Å, α= 102.95(2), β= 97.71(2), γ= 80.95(2)°, and Z= 2 for the [NBuⁿ₄]⁺ salt and a= 15.416(3), b= 15.976(3), c= 16.106(4)Å, α= 93.32(2), β= 101.41 (2), γ= 56.60(1)°, and Z= 4 for the [Fe(C₅Me₅)₂]⁺ salt. Leastsquares refinements, based on 3770 and 7069 reflections [|F_o| > 3σ(F)] converged at R= 0.075 and 0.067, respectively. The complexes were oxidized upon treatment with iodine, [ttf]₃[BF₄]₂(ttf˙⁺= the radical cation of tetrathiafulvalene), [Fe(C₅H₅)₂][PF₆], or [Fe(C₅Me₅)₂][BF₄] and by current-controlled electrolysis to afford partially oxidized [Fe(C₃S₅)₂]^n– and [Fe(C₃Se₅)₂]^n–(n= 0.05–0.7) species. The oxidized C₃S₅ complexes exhibit electrical conductivities of 1.9 × 10^–5–1.0 × 10^–1S cm^–1 and the oxidized C₃Se₅ complexes 5.9 × 10^–8–1.1 × 10^–2 S cm^–1 at room temperature as compacted pellets. Ligand centred oxidation is deduced to occur for the partially oxidized complexes on the basis of IR, ESR, and X-ray photoelectron spectra.