Synthesis and Properties of Iron(II) Hydride Complexes Containing the Tripodal Tetraphosphine Ligand...

The preparation and characterization of iron(II) hydride complexes containing the tripodal tetraphosphine ligand tris[2-(dimethylphosphino)ethyl]phosphine, P(CH(2)CH(2)PMe(2))(3) (PP(3)), 1, are reported. Dissolution of the chloro hydride complex FeHCl(PP(3)), 2, in methanol affords an equilibrium mixture of 2 and the methoxy hydrido complex FeH(OMe)(PP(3)), 3. Reaction of a methanol solution containing 2 and 3 with anionic or neutral ligands affords the corresponding hydrido complexes: reaction with NaBr affords FeHBr(PP(3)), 4; reaction with NaI affords FeHI(PP(3)), 5; reaction with NaN(3) affords FeHN(3)(PP(3)), 6; reaction with CO affords [FeH(CO)(PP(3))](+), 7; reaction with N(2) affords [FeH(N(2))(PP(3))](+), 8; and reaction with PPh(3) affords [FeHPPh(3)(PP(3))](+), 9. In some cases, further reaction of the product iron hydride complexes is observed. Reaction of FeHN(3)(PP(3)), 6, with NaN(3) for an extended period affords Fe(N(3))(2)(PP(3)), 10. On standing in solution, [FeH(N(2))(PP(3))](+), 8, is converted to the dinitrogen-bridged complex [FeH(PP(3))N&tbd1;NFeH(PP(3))](2+), 11. The carbonyl hydride complex 7 and the dinitrogen hydride complex 8 can be deprotonated to give the neutral iron(0) complexes Fe(CO)(PP(3)), 12, and Fe(N(2))(PP(3)), 13, respectively. The air-sensitive complexes 4-13 were characterized, by multinuclear NMR, IR, Raman, and mass spectroscopy and by elemental analysis.