SYNTHESIS OF TETRAMETALLIC THIOLATE-BRIDGED FE3AU CLUSTERS - CRYSTAL-STRUCTURE OF [FE3(CO)9(MU-3-SPRI)(MU-AU(PPH3))]

The reaction of the lithium salt of [Fe3(CO)9(mu3-SR)]- with [Au(PPh3)Cl], in the presence of TlBF4, gives high yields of the new tetrametallic clusters [Fe3(CO)9(mu3-SR){mu-Au(PPh3)}] (R = Pr(i) 1, Bu(t) 2, C6H11 3 or Et 4). Clusters 3 and 4 were formed along with the dimetallic species [Fe2(CO)6(mu-CO)(mu-SR){mu-Au(PPh3)}] (R = C6H11 5 or Et 6). The structure of 1 has been determined by X-ray diffraction methods. The metal core consists of an isosceles triangle of iron atoms, capped by a SPr(i) ligand and the longest iron-iron bond is bridged by an Au(PPh3) fragment. The fast atom bombardment mass spectra of the positive ions of 1-4 show a similar pattern to that reported for [Fe3(CO)9(mu3-SR)(mu-H)] consisting of a primary fragmentation involving stepwise loss of carbonyl groups from the parent ion to give [Fe3-(SR){Au(PPh3)}]+, followed by elimination of an olefinic group to give [Fe3(SH){Au(PPh3)}]+ and finally loss of hydrogen to afford [Fe3(S){Au(PPh3)}]+.