Chlorobis(dppe)iron hydride explained

Chlorobis(dppe)iron hydride is a coordination complex with the formula HFeCl(dppe)2, where dppe is the bidentate ligand 1,2-bis(diphenylphosphino)ethane. It is a red-violet solid. The compound has attracted much attention as a precursor to dihydrogen complexes.[1]

Structure

The complex exhibits octahedral molecular geometry. The chloride and hydride ligands are mutually trans.[2] The bond distances between the iron metal atom and the coordinating ligands are given by the following:

Bond Bond distance
Fe-P1 2.238
Fe-P2 2.256
Fe-P3 2.236
Fe-P4 2.255
Fe-Cl 2.404
Fe-H 1.313

Synthesis and reactions

The compound is synthesized according to the following idealized reaction:[3]

FeCl2 + 2 dppe + Na[BH<sub>4</sub>] → NaCl + ½ B2H6 + HFeCl(dppe)2In the course of this conversion, high-spin complex FeCl2(dppe)2 converts to low-spin HFeCl(dppe)2.

The complex HFeCl[(dppe)<sub>2</sub> exhibits a number of reactions associated with the remaining Fe-Cl bond. Reaction of the complex with [[sodium borohydride]] gives the dihydride complex:

HFeCl(dppe)2 + NaBH4 → H2Fe(dppe)2 + NaCl + "BH3"

Removal of chloride using sodium tetrafluorborate under and atmostphere of hydrogen or nitrogen gives the dinitrogen and dihydrogen complexes:[4]

Notes and References

  1. Morris RH . Dihydrogen, Dihydride and in Between: Nmr and Structural Properties of Iron Group Complexes . Coord. Chem. Rev. . 2008 . 2252 . 21–22 . 2381–2394 . 10.1016/j.ccr.2008.01.010.
  2. Lee, J.; Jung, G.; Lee, S. W. Structure of trans-chlorohydridobis(diphenylphosphinoethane)iron(II). Bull. Korean. Chem. 1998, 19, 267.
  3. Book: Giannoccaro, P. . Sacco, A. . Inorganic Syntheses . Bis[Ethylenebis(Diphenylphosphine)]-Hydridoiron Complexes . Inorg. Synth.. 1977. 17. 69–71. 10.1002/9780470132487.ch19. 9780470132487 .
  4. Bautista MT, Bynum LD, Schauer CK . Synthesis of η2-Dihydrogen Complex, trans-[BF<sub>4</sub>]: An Experiment for an Advanced Inorganic Chemistry Laboratory Involving Synthesis and NMR Properties of an η2-H2 Complex |journal=Journal of Chemical Education |year=1996 |volume=73 |issue=10 |pages=988–991 |doi=10.1021/ed073p988}}

    HFeCl(dppe)2 + NaBF4 + N2 → [HFe(N<sub>2</sub>)(dppe)<sub>2</sub>]BF4 + NaCl

    HFeCl(dppe)2 + NaBF4 + H2 → [HFe(H<sub>2</sub>)(dppe)<sub>2</sub>]BF4 + NaCl

    References

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