647823-71-0Relevant articles and documents
New routes to low-coordinate iron hydride complexes: The binuclear oxidative addition of H2
Dugan, Thomas R.,Holland, Patrick L.
, p. 2825 - 2830 (2009/12/09)
The oxidative addition and reductive elimination reactions of H2 on unsaturated transition-metal complexes are crucial in utilizing this important molecule. Both biological and man-made iron catalysts use iron to perform H2 transform
The reactivity patterns of low-coordinate iron-hydride complexes
Yu, Ying,Sadique, Azwana R.,Smith, Jeremy M.,Dugan, Thomas R.,Cowley, Ryan E.,Brennessel, William W.,Flaschenriem, Christine J.,Bill, Eckhard,Cundari, Thomas R.,Holland, Patrick L.
, p. 6624 - 6638 (2008/12/22)
We report a survey of the reactivity of the first isolable iron-hydride complexes with a coordination number less than 5. The high-spin iron(II) complexes [(β-diketiminate)Fe(μ-H)]2 react rapidly with representative cyanide, isocyanide, alkyne, N2, alkene, diazene, azide, CO2, carbodiimide, and Bronsted acid containing substrates. The reaction outcomes fall into three categories: (1) addition of Fe-H across a multiple bond of the substrate, (2) reductive elimination of H2 to form iron(I) products, and (3) protonation of the hydride to form iron(II) products. The products include imide, isocyanide, vinyl, alkyl, azide, triazenido, benzo[c]cinnoline, amidinate, formate, and hydroxo complexes. These results expand the range of known bond transformations at iron complexes. Additionally, they give insight into the elementary transformations that may be possible at the iron-molybdenum cofactor of nitrogenases, which may have hydride ligands on high-spin, low-coordinate metal atoms.
Synthesis and reactivity of low-coordinate iron(II) fluoride complexes and their use in the catalytic hydrodefluorination of fluorocarbons
Vela, Javier,Smith, Jeremy M.,Yu, Ying,Ketterer, Nicole A.,Flaschenriem, Christine J.,Lachicotte, Rene J.,Holland, Patrick L.
, p. 7857 - 7870 (2007/10/03)
Transition metal fluoride complexes are of interest because they are potentially useful in a multitude of catalytic applications, including C-F bond activation and fluorocarbon functionalization. We report the first crystallographically characterized examples of molecular iron(II) fluorides: [LMeFe(μ-F)]2 (12) and LtBuFeF (2) (L = bulky β-diketiminate). These complexes react with donor molecules (L'), yielding trigonal-pyramidal complexes LRFeF(L'). The fluoride ligand is activated by the Lewis acid Et2O·BF3, forming LtBuFe(OEt2)(η1-BF4) (3), and is also silaphilic, reacting with silyl compounds such as Me 3SiSSiMe3, Me3SiCCSiMe3, and Et 3SiH to give new thiolate LtBuFeSSiMe3 (4), acetylide LtBuFeCCSiMe3 (5), and hydride [L MeFe(μ-H)]2 (62) complexes. The hydrodefluorination (HDF) of perfluorinated aromatic compounds (hexafluorobenzene, pentafluoropyridine, and octafluorotoluene) with a silane R3SiH (R3 = (EtO)3, Et3, Ph 3, (3,5-(CF3)2C6H 3)Me2) is catalyzed by addition of an iron(II) fluoride complex, giving mainly the singly hydrodefluorinated products (pentafluorobenzene, 2,3,5,6-tetrafluoropyridine, and α,α,α,2, 3,5,6-heptafluorotoluene, respectively) in up to five turnovers. These catalytic perfluoroarene HDF reactions proceed with activation of the C-F bond para to the most electron-withdrawing group and are dependent on the degree of fluorination and solvent polarity. Kinetic studies suggest that hydride generation is the rate-limiting step in the HDF of octafluorotoluene, but the active intermediate is unknown. Mechanistic considerations argue against oxidative addition and outer-sphere electron transfer pathways for perfluoroarene HDF. Fluorinated olefins are also hydrodefluorinated (up to 10 turnovers for hexafluoropropene), most likely through a hydride insertion/β-fluoride elimination mechanism. Complexes 12 and 2 thus provide a rare example of a homogeneous system that activates C-F bonds without competitive C-H activation and use an inexpensive 3d transition metal.
