2 SILICON-BRIDGED CYCLOPENTADIENYL FE2S4 CLUSTER UNITS CONNECTED THROUGH AN FE(III)S6 UNIT - CRYSTAL AND MOLECULAR-STRUCTURE OF H3)2SICP'2)2FE5(MU-3-S2)2(MU-4-S2)2(MU-4-S4)]FECL4

The reaction Of (CH3)2Si[Cp'Fe(CO)2]2 with elemental sulfur in refluxi ng toluene resulted in the formation of two new iron-sulfur cluster co mpounds. Prolonged crystallisation from CH2Cl2-hexane mixtures of one of these compounds resulted in crystals of the title compound. An X-ra y diffraction study revealed that two (CH3)2SiCp2'Fe2 units are connec ted to a central Fe(III) ion via four disulfido ligands and a tetrasul fido ligand. This iron atom is octahedrally coordinated by six sulfur atoms. Of the six Fe(III)-S distances four are close to 2.30 angstrom and the other two are about 2.20 angstrom. In both the (CH3)2SiCp2'Fe2 units each iron atom is coordinated to three sulfur atoms and one Cp ring. This results in twelve Fe-S distances: six of them are in a narr ow range from 2.165 to 2.184 A, whereas the other six vary from 2.240 to 2.286 angstrom. The Fe-Fe distances are 2.561 and 2.581 angstrom. T he S-S distances range from 2.041 to 2.073 angstrom. The Fe-Cl distanc es in the FeCl4- ion, centred around 2.16 angstrom show the presence o f Fe(III) in this ion.