Synthesis and Decarbonylation Reactions of the Triiron Phosphinidene Complex [Fe3Cp3(μ-H)(μ3-PPh)(CO)4]: Easy Cleavage and Formation of P–H and Fe–Fe Bonds

The binuclear phosphine complex [Fe2Cp2(μ-CO)2(CO)(PH2Ph)] (Cp = η5-C5H5) reacted with the acetonitrile adduct [Fe2Cp2(μ-CO)2(CO)(NCMe)] in dichloromethane at 293 K to give the trinuclear hydride–phosphinidene derivative [Fe3Cp3(μ-H)(μ3-PPh)(CO)4] as a mixture of cis,anti and trans isomers (Fe–Fe = 2.7217(6) Å for the cis,anti isomer). In contrast, photochemical treatment of the phosphine complex with [Fe2Cp2(CO)4] gave the phosphide-bridged complex trans-[Fe3Cp3(μ-PHPh)(μ-CO)2(CO)3] as the major product, along with small amounts of the binuclear hydride–phosphide complexes [Fe2Cp2(μ-H)(μ-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(μ-H)(μ3-PPh)(μ-CO)2] (Fe–Fe = 2.592(2)–2.718(2) Å); (b) the 50-electron complex [Fe3Cp3(μ-H)(μ3-PPh)(μ-CO)(CO)2], also having carbonyl- and hydride-bridged metal–metal bonds (Fe–Fe = 2.6177(3) and 2.7611(4) Å, respectively); and (c) the 48-electron phosphide cluster [Fe3Cp3(μ-PHPh)(μ3-CO)(μ-CO)2], an isomer of the latter phosphinidene complex now having three intermetallic bonds (Fe–Fe = 2.5332(8)–2.6158(8) Å).