Formation and reactivity of gaseous iron-sulfur clusters

The gas-phase reactions of Fe-n(+) clusters, n = 1-6, with COS and CS2 have been investigated by means of Fourier-transform ion-cyclotron resonance mass spectrometry. Whereas CS2 predominantly substitutes one Fe atom, COS exclusively affords multiple sulfur transfer and thus opens a synthetic route to gaseous FenSx+ clusters. In the final products such as Fe2S2+, Fe3S2+, and Fe4S4+, the sulfur atoms appear to occupy multiple coordination sites much like in the analogous biogeneous iron-sulfur clusters. Bracketing experiments find IE(Fe2S2) = 7.2+/-0.3 eV besides providing upper limits for IE(Fe3S2) and IE(Fe4S4). In accordance with the low IE(Fe2S2), Fe2S2+ does not activate H-2 or small hydrocarbons and only exhibits rather limited reactivity towards more reactive substrates. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).