Synthesis and Properties of Iron(II) Hydride Complexes Containing the Tripodal Tetraphosphine Ligand P(CH(2)CH(2)PMe(2))(3).

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)), 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.