Publication

Article Metrics

Citations


Online attention

Hard X-ray spectroscopy: An exhaustive toolbox for mechanistic studies (?)

DOI: 10.1039/C9FD00070D DOI Help

Authors: Anke Schoch (Paderborn University) , Lukas Burkhardt (Paderborn University) , Roland Schoch (Paderborn University) , Kai Stuehrenberg (Paderborn University) , Matthias Bauer (Paderborn University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Faraday Discussions

State: Published (Approved)
Published: June 2019

Abstract: Established and recent hard X-ray spectroscopic methods in form of conventional X-ray absorption near edge structure spectroscopy (XANES) and extended X-ray absorption fine structure spectroscopy (EXAFS), and the photon-in/photon-out techniques high energy resolution fluorescence detected XANES and valence-to-core X-ray emission spectroscopy (VtC-XES) provide unique opportunities to study mechanisms in metal-organic reactions. The combination of these techniques allows the determination of the local geometric and electronic structure in form of the numbers of nearest neighbours, their types and distances around an X-ray absorbing atom and the highest occupied and lowest unoccupied molecular levels. Different sample cells for this purpose, which allow high pressure, electrochemical or multi-spectroscopic measurements under inert conditions, are presented and discussed. The potential of HERFD-XANES and VtC-XES to eliminate limitations of conventional EXAFS spectroscopy is established with case studies on the Hieber anion [Fe(CO)3(NO)]- and the iron hydride complex [Fe(CO)H(NO)(PPh3)2]. With VtC-XES the formation of an allyl complex by reaction of [Fe(CO)3(NO)]- in a catalytic nucleophilic substitution reaction can be followed. Combination of HERFD-XANES and VtC-XES allows the identification and investigation of hydride species, as well as their fate in chemical reaction. On the other hand, in order to investigate the active species formation in iron-catalysed cross coupling reactions, conventional XANES and EXAFS are the method of choice for the moment. For all examples, the advantages and limitations of the hard X-ray toolbox are commented and the value of the individual methods are compared.

Subject Areas: Technique Development, Physics


Instruments: B18-Core EXAFS

Other Facilities: ESRF; PETRA III