Recent XAS studies into Homogeneous metal catalyst in fine chemical and pharmaceutical syntheses

Abstract

A brief review of studies using X-ray Absorption Spectroscopy (XAS) to investigate homogeneous catalytic reactions in fine chemical and pharmaceutical context since 2010 is presented. The advantages of the techniques over traditional lab-based analytical tools, particularly when NMR spectroscopy fails to deliver mechanistic insights, are summarised using these examples. A discussion on the current limitations of the techniques and challenges in the near future is also included.Graphical abstractA minireview of recent developments in application of X-ray Absorption Spectroscopy as an effective mechanistic tool to synthetic catalytic reactions relevant to fine chemical and pharmaceutical syntheses.

Operando Spectroscopic and Kinetic Characterization of Aerobic Allylic C–H Acetoxylation Catalyzed by Pd(OAc)2/4,5-Diazafluoren-9-one

“…The data noted above imply that the oxidation state of the Pd catalyst changes during the course of the reaction. Palladium K-edge X-ray absorption spectroscopy probes the excitation of Pd 1s electrons, and the “near edge” absorption energy, corresponding to the 1s→5p orbital transition, provides insight into the oxidation state of Pd complexes. , This technique has been used to probe a number of homogeneous Pd-catalyzed reactions, − including recent analysis of a Pd-catalyzed aerobic oxidation of an aromatic C–H bond . In order to conduct analogous experiments for the allylic acetoxylation reaction, a reactor was designed and constructed to enable operando studies on the high photon-flux beamline at Argonne National Laboratories (see Supporting Information for details; Figures S3–S6).…”

Operandomonitoring of mechanisms and deactivation of molecular catalysts

“…60,61 It is widely used in heterogeneous operando studies, however, only few cases have been presented on molecular catalysis in situ analysis. [62][63][64][65][66] Among one of the first in situ XAS studies is a study on the bromobenzene homocoupling with a [Ni(cod) (bpy)] by Tanaka's group. 67 Using time-resolved XANES and EXAFS analysis they were able to monitor the reactant [Ni(cod) (bpy)], the intermediate [Ni(bpy)(Ph)Br(DMF) 2 ] and the subproduct [Ni(bpy)Br 2 (DMF)] 2 .…”

Real-space Green's function approach for x-ray spectra at high temperature

“…X-ray absorption spectroscopy (XAS) has become an important tool for studies of materials in fields ranging from materials science and chemistry to geophysics and astrophysics [1][2][3][4][5][6]. XAS is used extensively to probe both local electronic and structural properties simultaneously at synchrotron facilities worldwide.…”