Halide coordinated homoleptic [Fe4S4X4]2− and heteroleptic [Fe4S4X2Y2]2− clusters (X, Y = Cl, Br, I)-alternative preparations, structural analogies and spectroscopic properties in solution and solid stateElectronic supplementary information (ESI) available: Negative mode ESI mass and UV-vis-NIR spectra as well as synchrotron XRPD as mentioned in the text. See DOI: 10.1039/c5dt02769a

• Main Authors: Schüren, Andreas O, Gramm, Verena K, Dürr, Maximilian, Foi, Ana, Ivanovi -Burmazovi, Ivana, Doctorovich, Fabio, Ruschewitz, Uwe, Klein, Axel
• Format: Article
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c5dt02769a

New facile methods to prepare iron sulphur halide clusters [Fe 4 S 4 X 4 ] 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 [Fe 4 S 4 X 4 ] 2− (X = Cl, Br) and heteroleptic clusters [Fe 4 S 4 X 4− n Y n ] 2− (X = Cl, Br; Y = Br, I). Solid materials were obtained as salts of BTMA + (= benzyltrimethylammonium); the new compounds containing [Fe 4 S 4 Br 4 ] 2− and [Fe 4 S 4 X 2 Y 2 ] 2− (X, Y = Cl, Br, I) were all isostructural to (BTMA) 2 [Fe 4 S 4 I 4 ] (monoclinic, Cc ) as inferred from synchrotron 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 [Fe 4 S 4 X 4− n Y n ] 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. Iron sulphur halide clusters [Fe 4 S 4 X 4 ] 2− and [Fe 4 S 4 X 2 Y 2 ] 2− were synthesised and characterised using HR-MS and UV-vis-NIR in solution and using IR and synchrotron XRPD in the solid.