COORDINATIVELY UNSATURATED COMPLEXES [FE2(CO)5(MU-PBUT2)(MU-PR2)](FE=FE) (R=CY, PH) - ADDITION OF PBUN3, PH2PH, AND DPPM (DPPM = BIS(DIPHENYLPHOSPHINO)METHANE) - THE UNPRECEDENTED COMPLEX [FE2(CO)3(MU-PBUT2)(MU-PCY2)(MU-DPPM)](FE-FE)

A convenient synthesis of the saturated complexes [Fe2(CO)6(mu-PBu(t)2)(mu-PR2)] (R = Cy (4), Ph (5)) and their photochemical in situ transformation into the corresponding unsaturated diiron pentacarbonyl complexes 2 and 3 are described. These compounds readily add PBu(n)3 and Ph2PH, respectively, in the molar ratio 1:1 to give the complexes [Fe2(CO)5(mu-PBu(t)2)(mu-PR2)(PR'2R'')] (R = Cy, R' = R'' = Bu(n) (6); R' = Ph, R'' = H (7); R = R' = Ph, R'' = H (8)). Complex 6 reacts under UV irradiation with excess PBu(n)3 to afford the complex [Fe2(CO)4-(mu-PBu(t)2)(mu-PCy2)(PBu(n)3)2] (9). Treatment of 2 with dppm (dppm = bis(diphenylphosphino)methane) gives after subsequent photolysis the unprecedented triply-bridged complex [Fe2(CO)3(mu-PBu(t)2)(mu-PCy2)(mu-dppm)](10). Complex 10, formally belonging to the complexes of general formula [Fe2L5(mu-PR2)2] (L = 2e ligand) with an iron-iron double bond, shows only an iron-iron single bond distance (2.631(1) angstrom) due to the bent Fe2(mu-P[)2 core (theta = 107.6-degrees) caused by the bridging dppm ligand. The molecular structures of complexes 6, 7, and 10 are described.