Synthesis and properties of iron(II) hydride complexes containing the tripodal tetraphosphine ligand P(CH2CH2PMe2)3

The preparation and characterization of iron(II) hydride complexes containing the tripodal tetraphosphine ligand tris[2-(dimethylphosphino)ethyl]phosphine, P(CH2CH2PMe2)(3) (PP3), 1, are reported. Dissolution of the chloro hydride complex FeHCl(PP3), 2, in methanol affords an equilibrium mixture of 2 and the methoxy hydrido complex FeH(OMe)(PP3), 3. Reaction of a methanol solution containing 2 and 3 with anionic or neutral ligands affords the corresponding hydride complexes: reaction with NaBr affords FeHBr(PP3), 4; reaction with NaI affords FeHI(PB3), 5; reaction with NaN3 affords FeHN3(PP3), 6; reaction with CO affords [FeH(CO)(PP3)](+), 7; reaction with N-2 affords [FeH(N-2)(PP3)](+), 8; and reaction with PPh3 affords [FeHPPh3(PP3)](+); 9. In some cases, further reaction of the product iron hydride complexes is observed. Reaction of FeHN3(PP3), 6, with NaN3 for an extended period affords Fe(N-3)(2)(PP3), 10 On standing in solution, [FeH(N-2)(PP3)](+), 8, is converted to the dinitrogen-bridged complex [FeH(PP3)N drop NFeH(PP3)](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)(PP3), 12, and Fe(N-2)(PP3), 13, respectively. The air-sensitive complexes 4-13 were characterized, by multinuclear NMR, IR, Raman, and mass spectroscopy and by elemental analysis.