Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Orbital-specific mapping of the ligand exchange dynamics of Fe(CO)5 in solution


Transition-metal complexes have long attracted interest for fundamental chemical reactivity studies and possible use in solar energy conversion1,2. Electronic excitation, ligand loss from the metal centre, or a combination of both, creates changes in charge and spin density at the metal site3,4,5,6,7,8,9,10,11 that need to be controlled to optimize complexes for photocatalytic hydrogen production8 and selective carbon–hydrogen bond activation9,10,11. An understanding at the molecular level of how transition-metal complexes catalyse reactions, and in particular of the role of the short-lived and reactive intermediate states involved, will be critical for such optimization. However, suitable methods for detailed characterization of electronic excited states have been lacking. Here we show, with the use of X-ray laser-based femtosecond-resolution spectroscopy and advanced quantum chemical theory to probe the reaction dynamics of the benchmark transition-metal complex Fe(CO)5 in solution, that the photo-induced removal of CO generates the 16-electron Fe(CO)4 species, a homogeneous catalyst12,13 with an electron deficiency at the Fe centre14,15, in a hitherto unreported excited singlet state that either converts to the triplet ground state or combines with a CO or solvent molecule to regenerate a penta-coordinated Fe species on a sub-picosecond timescale. This finding, which resolves the debate about the relative importance of different spin channels in the photochemistry of Fe(CO)5 (refs 4, 16,17,18,19 and 20), was made possible by the ability of femtosecond X-ray spectroscopy to probe frontier-orbital interactions with atom specificity. We expect the method to be broadly applicable in the chemical sciences, and to complement approaches that probe structural dynamics in ultrafast processes.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout

Figure 1: Scheme and results of the experiment.
Figure 2: Fe-specific changes in the electronic structure of Fe(CO)4 after femtosecond spin crossover and ligation.
Figure 3: Schematic reaction pathways of Fe(CO)4 in EtOH.


  1. Parshall, G. W. Organometallic chemistry in homogeneous cata1ysis. Science 208, 1221–1224 (1980).

    Article  CAS  ADS  Google Scholar 

  2. Gray, H. B. & Maverick, A. W. Solar chemistry of metal complexes. Science 214, 1201–1205 (1981).

    Article  CAS  ADS  Google Scholar 

  3. Bengali, A. A., Bergman, R. G. & Moore, C. B. Evidence for the formation of free 16-electron species rather than solvate complexes in the ultraviolet irradiation of CpCo(CO)2 in liquefied noble gas solvents. J. Am. Chem. Soc. 117, 3879–3880 (1995).

    Article  CAS  Google Scholar 

  4. Snee, P. T., Payne, C. K., Mebane, S. D., Kotz, K. T. & Harris, C. B. Dynamics of photosubstitution reactions of Fe(CO)5: an ultrafast infrared study of high spin reactivity. J. Am. Chem. Soc. 123, 6909–6915 (2001).

    Article  CAS  Google Scholar 

  5. Besora, M. et al. A combined theoretical and experimental study on the role of spin states in the chemistry of Fe(CO)5 photoproducts. J. Am. Chem. Soc. 131, 3583–3592 (2009).

    Article  CAS  Google Scholar 

  6. Juban, E. A., Smeigh, A. L., Monat, J. E. & McCusker, J. K. Ultrafast dynamics of ligand-field excited states. Coord. Chem. Rev. 250, 1783–1791 (2006).

    Article  CAS  Google Scholar 

  7. Chergui, M. On the interplay between charge, spin and structural dynamics in transition metal complexes. Dalton Trans. 41, 13022–13029 (2012).

    Article  CAS  Google Scholar 

  8. Heyduk, A. F. & Nocera, D. G. Hydrogen produced from hydrohalic acid solutions by a two-electron mixed-valence photocatalyst. Science 293, 1639–1641 (2001).

    Article  CAS  ADS  Google Scholar 

  9. Arndtsen, B. A., Bergman, R. G., Mobley, T. A. & Peterson, T. H. Selective intermolecular carbon–hydrogen bond activation by synthetic metal complexes in homogeneous solution. Acc. Chem. Res. 28, 154–162 (1995).

    Article  CAS  Google Scholar 

  10. Labinger, J. A. & Bercaw, J. E. Understanding and exploiting C–H bond activation. Nature 417, 507–514 (2002).

    Article  CAS  ADS  Google Scholar 

  11. Bromberg, S. E. et al. The mechanism of a C–H bond activation reaction in room-temperature alkane solution. Science 278, 260–263 (1997).

    Article  CAS  Google Scholar 

  12. Wrighton, M. S., Ginley, D. S., Schroeder, M. A. & Morse, D. L. Generation of catalysts by photolysis of transition metal complexes. Pure Appl. Chem. 41, 671–687 (1975).

    Article  CAS  Google Scholar 

  13. Whetten, R. L., Fu, K.-J. & Grant, E. R. Pulsed-laser photocatalytic isomerization and hydrogenation of olefins. J. Am. Chem. Soc. 104, 4270–4272 (1982).

    Article  CAS  Google Scholar 

  14. Langmuir, T. Types of valence. Science 54, 59–67 (1921).

    Article  CAS  ADS  Google Scholar 

  15. Hoffmann, R. Building bridges between inorganic and organic chemistry. Angew. Chem. Int. Edn Engl. 21, 711–724 (1982).

    Article  Google Scholar 

  16. Poliakoff, M. & Turner, J. J. The structure of [Fe(CO)4]—an important new chapter in a long-running story. Angew. Chem. Int. Edn Engl. 40, 2809–2812 (2001).

    Article  CAS  Google Scholar 

  17. Trushin, S. A., Fuss, W., Kompa, K. L. & Schmid, W. E. Femtosecond dynamics of Fe(CO)5 photodissociation at 267 nm studied by transient ionization. J. Phys. Chem. A 104, 1997–2006 (2000).

    Article  CAS  Google Scholar 

  18. Ihee, H., Cao, J. & Zewail, A. H. Ultrafast electron diffraction of transient [Fe(CO)4]: determination of molecular structure and reaction pathway. Angew. Chem. Int. Edn Engl. 40, 1532–1536 (2001).

    Article  CAS  Google Scholar 

  19. Snee, P. T., Payne, C. K., Kotz, K. T., Yang, H. & Harris, C. B. Triplet organometallic reactivity under ambient conditions: an ultrafast UV pump/IR probe study. J. Am. Chem. Soc. 123, 2255–2264 (2001).

    Article  CAS  Google Scholar 

  20. Ahr, B. et al. Picosecond X-ray absorption measurements of the ligand substitution dynamics of Fe(CO)5 in ethanol. Phys. Chem. Chem. Phys. 13, 5590–5599 (2011).

    Article  CAS  Google Scholar 

  21. Nayak, S. K., Farrell, G. J. & Burkey, T. J. Photosubstitution of two iron pentacarbonyl CO's in solution via a single-photon process: dependence on dispersed ligands and role of triplet intermediates. Inorg. Chem. 33, 2236–2242 (1994).

    Article  CAS  Google Scholar 

  22. Zhang, W. et al. Tracking excited-state charge and spin dynamics in iron coordination complexes. Nature 509, 345–348 (2014).

    Article  CAS  ADS  Google Scholar 

  23. Bressler, C. et al. Femtosecond XANES study of the light-induced spin crossover dynamics in an iron(II) complex. Science 323, 489–492 (2009).

    Article  CAS  ADS  Google Scholar 

  24. Huse, N. et al. Femtosecond soft X-ray spectroscopy of solvated transition-metal complexes: deciphering the interplay of electronic and structural dynamics. J. Phys. Chem. Lett. 2, 880–884 (2011).

    Article  CAS  Google Scholar 

  25. Portius, P. et al. Unraveling the photochemistry of Fe(CO)5 in solution: observation of Fe(CO)3 and the conversion between 3Fe(CO)4 and 1Fe(CO)4(solvent). J. Am. Chem. Soc. 126, 10713–10720 (2004).

    Article  CAS  Google Scholar 

  26. Joly, A. G. & Nelson, K. A. Metal carbonyl photochemistry in organic solvents: femtosecond transient absorption and preliminary resonance Raman spectroscopy. Chem. Phys. 152, 69–82 (1991).

    Article  CAS  Google Scholar 

  27. Fukui, K. The role of frontier orbitals in chemical reactions. Angew. Chem. Int. Edn Engl. 21, 801–809 (1982).

    Article  Google Scholar 

  28. Lim, M., Jackson, T. A. & Anfinrud, P. A. Binding of CO to myoglobin from a heme pocket docking site to form nearly linear Fe–C–O. Science 269, 962–966 (1995).

    Article  CAS  ADS  Google Scholar 

  29. Nibbering, E. T. J., Fidder, H. & Pines, E. Ultrafast chemistry: using time-resolved vibrational spectroscopy for interrogation of structural dynamics. Annu. Rev. Phys. Chem. 56, 338–367 (2005).

    Article  ADS  Google Scholar 

  30. Greaves, S. J. et al. Vibrationally quantum-state-specific reaction dynamics of H atom abstraction by CN radical in solution. Science 331, 1423–1426 (2011).

    Article  CAS  ADS  Google Scholar 

Download references


This work was supported by the Volkswagen Stiftung (M.B.) the Swedish Research Council (M.O.), the Carl Tryggers Foundation (M.O.), the Magnus Bergvall Foundation (M.O.), the Collaborative Research Centers SFB 755 and SFB 1073 (I.R., S.G., W.Q., M.S. and S.T.) and the Helmholtz Virtual Institute ‘Dynamic Pathways in Multidimensional Landscapes’. W.Z., R.W.H. and K.J.G. acknowledge support through the AMOS program within the Chemical Sciences, Geosciences, and Biosciences Division of the Office of Basic Energy Sciences, Office of Science, US Department of Energy. Portions of this research were performed on the Soft X-ray Materials Science (SXR) Instrument at the Linac Coherent Light Source (LCLS), a division of SLAC National Accelerator Laboratory and an Office of Science user facility operated by Stanford University for the US Department of Energy. The SXR Instrument is funded by a consortium whose membership includes the LCLS, Stanford University through the Stanford Institute for Materials Energy Sciences (SIMES), Lawrence Berkeley National Laboratory (LBNL), the University of Hamburg through the BMBF priority program FSP 301, and the Center for Free Electron Laser Science (CFEL).

Author information

Authors and Affiliations



Ph.W., K.K., I.R., W.Q., M.B., S.S., D.N., W.F.S., J.J.T., F.H., S.T. and A.F. designed the experiment. Ph.W., K.K., I.R., W.Q., M.B., S.S., S.G., M.S., D.N., W.Z., R.W.H., W.F.S., J.J.T., B.K., F.H., K.J.G., S.T. and A.F. did the experiment. K.K., Ph.W., M.B. and A.F. analysed the experimental data. I.J., K.K. and M.O. performed the calculations. Ph.W., K.K. and K.J.G. wrote the manuscript with input from all authors.

Corresponding authors

Correspondence to Ph. Wernet, M. Odelius or A. Föhlisch.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Text, Supplementary Figures 1-14, Supplementary Tables 1-3, Supplementary References and Supplementary Acknowledgements. (PDF 2973 kb)

PowerPoint slides

Source data

Rights and permissions

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Wernet, P., Kunnus, K., Josefsson, I. et al. Orbital-specific mapping of the ligand exchange dynamics of Fe(CO)5 in solution. Nature 520, 78–81 (2015).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing