Collision-induced dissociation of [4Fe-4S] cubane cluster complexes: [Fe4S4Cl4 − x(SC2H5)x]2−/1− (x = 0-4)

Collision-induced dissociation (CID) experiments on a series of [4Fe-4S] cluster ions, [Fe4S4Cl4 − x(SC2H5)x]2−/1− (x = 0-4), revealed that their fragmentation channels change with the coordination environment. Among the three Coulomb repulsion related channels for the doubly charged species, the collision induced electron detachment channel was found to become more significant from x = 0 to 4 due to the decreasing electron binding energies and the magnitude of repulsion Coulomb barrier, while both the ligand detachment of Cl− and the fission of the [Fe4S4]2+ core became more and more significant with the increase of the Cl− coordination, and eventually became the dominant channel at x = 0. From the parents containing the SC2H5 ligand, neutral losses of HSC2H5 (62 u) and/or HSCHCH2 (60 u) were observed. It was proposed that inter- and intra-ligand proton transfer could happen during the CID process, resulting in hydrogen coordination to the [4Fe-4S] cluster. In the presence of O2, [Fe4S4Cl3(SC2H5)]2− and [Fe4S4Cl4]2− can form the O2-substituted products [Fe4S4Cl2(SC2H5)O2]− and [Fe4S4Cl3O2]−, respectively. It was shown that the O2 complexation occurs by coordination to the empty iron site of the [4Fe-4S] cubane core after dissociation of one Cl− ligand.