REACTIONS OF DI-ETA-5-CYCLOPENTADIENYLTRICARBONYLTRIPHENYL-PHOSPHINEDIIRON - AN IMPROVED SYNTHESIS OF THE CYCLOPENTADIENYLCARBONYLIRON TETRAMER

The compound (C5H5)2Fe2(CO)3PPh3, previously obtained by the photolysis of (C5H5)2Fe2(CO)4 with PPh3, may also be obtained by reflluxing these same reactants in benzene. The compound was isolated in pure form by means of low temperature column chromatography. It is unstable in solution in the absence of added PPh3. Solid samples also are unstable over long periods of time. Decomposition in solution is complete within one hour at 80° yielding a mixture of (C5H5)2Fe2(CO)4 and (C5H5)4Fe4(CO)4. This reaction is suppressed by excess PPh3. Heating a mixture of (C5H5)2Fe2(CO)3PPh3 and P(OEt)3 gives a nearly quantitative yield of (C5H5)2Fe2(CO)3P(OEt)3. Refluxing a xylene solution of (C5H5)2Fe2(CO)4 containing a slight molarr excess of PPh3 for 7 h results in the isolation of (C5H5)4Fe4(CO)4 in 56% yield, making this reaction by far the most convenient method for the preparation, in gram quantities, of this transition metal cluster. © 1979.