Ultraviolet photodissociation of gas-phase transition metal complexes: dicarbonylcyclopentadienyliodoiron(II)

Abstract

The ultraviolet photodissociation of the prototypical organometallic half-sandwich compound dicarbonylcyclopentadienyliodoiron(II) [η⁵-CpFe(CO)₂I] has been studied in the gas phase across the wavelength range 260 ≤ λ ≤ 310 nm using multi-mass velocity-map ion imaging with photoproducts detected using both resonance enhanced multiphoton and vacuum ultraviolet (λ = 118.2 nm) single photon ionisation methods. Ion images recorded for the atomic iodine and the cyclopentadienyl photoproducts reveal fast, anisotropic components to their recoil velocity distributions. The experimental work is supported by multi-reference (spin–orbit averaged) electronic structure calculations that suffice to illustrate the high electronic state density in such transition metal complexes and provide insights into the rival fragmentation dynamics. The ground state parent molecule has singlet spin multiplicity, but the product energy disposal measured following Fe–Cp bond fission shows the involvement of nominally spin-forbidden transitions. The Fe–I and Fe–Cp bond fissions should both be viewed as homolytic and occurring on excited state potentials that are dissociative in the relevant ligand elimination coordinate.

GRAPHICAL ABSTRACT

Keywords:

• Photodissociation
• organometallic complex
• velocity map ion imaging
• single photon ionisation
• multiphoton ionisation

Acknowledgments

The authors are grateful to the Engineering and Physical Sciences Research Council (EPSRC) for the award of a Programme Grant (EP/L005913) and to Emma Elsdon, Dr. Matthew Bain and Dr. James Smith for their many contributions to the earlier stages of this work. CSH is supported by an Australian Research Council Discovery Early Career Academic Award (DE200100549).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The raw ion events data and calculation log files can be retrieved from the University of Bristol’s research data repository and can be accessed using the following DOI: 10.5523/bris.3jmliakg8bki92w5k1908n7yks

Additional information

Funding

This work was supported by Australian Research Council [Grant Number DE200100549]; Engineering and Physical Sciences Research Council [Grant Number EP/L005913].