The binuclear phosphine complex [Fe2Cp2(mu-CO)(2)(CO)(PH2Ph)] (Cp = eta(5)-C5H5) reacted with the acetonitrile adduct [Fe2Cp2(mu-CO)(2)(CO)(NCMe)] in dichloromethane at 293 K to Stye the trinuclear hydride-phosphinidene derivative [Fe3Cp3(mu-H)(mu(3)-PPh)(CO)(4)] as a mixture of cis,anti and trans isomers (Fe-Fe = 2.7217(6) angstrom for the cis,anti isomer). In contrast, photochemical treatment of the phosphine complex with [Fe2Cp2(CO)(4)] gave the phosphide-bridged complex trans-[Fe3Cp3(mu-PHPh)(mu-CO)(2)(CO)(3)] as the major product, along with small amounts of the binuclear-hydride phosphide complexes [Fe2Cp2(mu-H)(mu-PHPh)(CO)(2)] (cis and trans isomers), which are more selectively prepared from [Fe2Cp2(CO)(4)] and PH2Ph at 388 K. The photochemical decarbonylation of either of the mentioned triiron compounds led reversibly to three different products depending on the reaction conditions: (a) the 48-electron phosphinidene cluster [Fe3Cp3(mu-H)(mu(3)-PPh)(mu-CO)(2)] (Fe-Fe = 2.592(2)-2.718(2) angstrom); (b) the 50-electron complex [Fe3Cp3(mu-H)(mu(3)-PPh)(mu-CO)(CO)(2)] also having carbonyl- and hydride-bridged metal-metal bonds (Fe-Fe = 2.6177(3) and 2.7611(4) angstrom, respectively); and (c) the 48-electron phosphide cluster [Fe3Cp3(mu-PHPh)(mu(3)-CO)(mu-CO)(2)], an isomer of the latter phosphinidene complex now having three intermetallic bonds (Fe-Fe = 2.5332(8)-2.6158(8) angstrom).