2020同步年報

Chemical Science 029 X -ray-absorption fine-structure (XAFS) spectra are widely em- ployed in heterogeneous catalysis, materials science, physics and related disciplines for the determination of element-speci c electronic and local geometric structure, but XAFS has been less commonly used for the characterization of organometallic reagents and homogeneous catalysts, especially under reaction conditions ( in situ or operando ). The team of Aiwen Lei and Yi-Hung Chen (Wuhan University, China) Fig. 1 : Plausible reaction mechanism for electrochemical oxidative aminocarbonylation of terminal alkynes. explore the catalytic cycles, along with various spectroscopic techniques. The detailed structural, dynamic and kinetic information (structure-reactiv- ity relations) contributes to the the- oretical basis for the optimization of a catalyst. A highly efficient catalytic system is extremely important for the environmental energy, pharmaceu- tical and fine chemical industry. As shown in Fig. 1 , two possible reaction paths for the palladium-catalyzed oxi- dative amino-carbonylation of alkynes have been reported. 1,2 All techniques used for mechanistic studies failed to provide structural information on the metal complexes and oxidation states during the catalytic cycle. Lei and his coworkers reported the first QXAFS scan of a solution of Pd(OAc) 2 and P( p -Tol) 3 in acetonitrile that was treated with phenylacety- lene, n -butylamine and Et 3 N under a CO atmosphere. The spectrum has perfect overlap in both the X-ray ab- sorption near-edge structure (XANES) ( Fig. 3 , blue line) and the extended X-ray-absorption fine-structure (EXAFS) spectra ( Fig. 2(a) , blue line) with experiment ex situ (the solution of Pd(OAc) 2 , P( p -Tol) 3 and n -butylamine Hard X-ray Spectroscopy: Verification of the Active Species in Pd-Catalyzed Reactions Rapid-scanning X-ray-absorption fine-structure spectra revealed the catalytic path of a palladi- um-catalysed oxidative carbonylation reaction under electrochemical conditions. applications in lattice, charge, spin and orbital degrees of freedom. (Reported by Jin-Ming Chen) This report features the work of Jin-Ming Chen and his col- laborators published in J. Am. Chem. Soc. 142 , 5731 (2020). This paper was selected as a cover of issue 12. SP 12U1 IXS • XES, PFY-XAS • Materials Science, Chemistry, Condensed-matter Physics devoted the use of the quick XAFS (QXAFS) technique at TPS 44A to study the structure of key intermedi- ates (coordination, oxidation state, electronic structure and geometry) of transition-metal catalysts in cross-cou- pling reactions. Three key features of their projects follow. (1) The cus- tom-made reaction cell was designed for reactions to demonstrate the laboratory procedures on the beam- line. (2) Time scale ms or μs is required for the study of fractional composition of these species during experiments in situ . (3) QXAFS was used mainly to Reference 1. Z. Liu, Y. Sakai, J. Yang, W. Li, Y. Liu, X. Ye, S. Qin, J. M. Chen, S. Agrestini, K. Chen, S.-C. Liao, S.-C. Haw, F. Baudelet, H. Ishii, T. Nishikubo, H. Ishizaki, T. Yamamoto, Z. Pan, M. Fukuda, K. Ohashi, K. Matsuno, A. Machida, T. Watanuki, S. I. Kawaguchi, A. M. Arevalo-Lopez, C. Jin, Z. Hu, J. P. Attfield, M. Azuma, Y. Long, J. Am. Chem. Soc. 142 , 5731 (2020).