CHEMICAL BEHAVIOR OF THE MIXED-METAL CARBONYL CLUSTERS [FE2RH(CO)(10)](-) AND [FE2RH2(CO)(12)](2-) - CRYSTAL-STRUCTURES OF [FE2RH(CO)(9)(PPH(3))](-) AND [FE2RH2(MU-CO)(3)(CO)(9)(MU(3)-AU(PPH(3)))](-)

Addition of triphenylphosphine to the cluster [Fe2Rh(CO)(10)](-) yield ed the derivative [Fe2Rh(CO)(9)(PPh(3))](-), which is stable enough to allow a single-crystal X-ray analysis on the [PPh(4)](+) salt. The cl uster contains a triangular metallic framework, the vertices of which are occupied by two Fe(CO)(4) groups and one Rh(CO)(PPh(3)) moiety; th e unsaturation of the cluster (46 valence electrons) is brought about by this 16-electron square-planar fragment. The cluster [Fe2Rh2(CO)(12 )](2-) was obtained by treating [Fe-2(Co)(9)] with [Rh(CO)(4)](-) (mol ar ratio 1:2) in refluxing acetone, and was characterized by infrared spectroscopy and elemental analyses. The adduct [Fe2Rh2(CO)(12){Au(PPh (3))}](-) was prepared by stoichiometric addition of [AU(PPh(3))Cl] in acetone and the crystal structure of the [PPh(4)](+) salt was elucida ted by X-ray analysis. The cluster contains a trigonal bipyramidal arr angement of metal atoms, with one Au(PPh(3)) and one Fe(CO)(3) group o ccupying the apical positions. The vertices of the FeRh2 equatorial pl ane are bound to two terminal carbonyl ligands, and the edges are span ned by three bridging carbonyls. The P-31 NMR spectral data for [Fe2Rh (CO)(9)(PPh(3))](-) and [Fe2Rh2(CO)(12){Au(PPh(3))}](-) are consistent with the solid-state structures, but do not exclude the presence of f luxional processes in solution.