Halide coordinated homoleptic [Fe4S4X4]; and heteroleptic [Fe4S4X2Y2] clusters (X, Y = Cl, Br, I)?alternative preparations, structural analogies and spectroscopic properties in solution and solid state

RUSCHEWITZ, U.; SCHÜREN, A. O.; FOI, A.; KLEIN, A.; DOCTOROVICH, F.; GRAMM, V. K.; IVANOVIC-BURMAZOVIC, I.

DALTON TRANSACTIONS

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2016

1477-9226

New facile methods to prepare iron sulphur halide clusters [Fe4S4X4]2− from [Fe(CO)5] and elemental sulphur were elaborated. Reactions of ferrous precursors like tetrahalidoferrates(II) or simple ferrous halides with [Fe(CO)5] and sulphur turned out to be efficient methods to prepare homoleptic [Fe4S4X4]2−(X = Cl, Br) and heteroleptic clusters [Fe4S4X4−nYn]2− (X = Cl, Br; Y = Br, I). Solid materials were obtained as salts of BTMA+ (= benzyltrimethylammonium); the new compounds containing [Fe4S4Br4]2− and [Fe4S4X2Y2]2− (X, Y = Cl, Br, I) were all isostructural to (BTMA)2[Fe4S4I4] (monoclinic, Cc) as inferred fromsynchrotron X-ray powder diffraction. While the solid materials contain defined heteroleptic clusters with a halide X : Y ratio of 2 : 2, dissolving these compounds leads to rapid scrambling of the halide ligands forming mixtures of all five possible [Fe4S4X4−nYn]2− clusters as could be shown by UHR-ESI MS. The variation of X and Y allowed assignment of the absorption bands in the visible and NIR; the long-wavelength bands around 1100 nm were tentatively assigned to intervalence charge transfer (IVCT) transitions.