Solution X-Ray Absorption Spectroscopy (XAS) for Analysis of Catalytically Active Species in Reactions with Ethylene by Homogeneous (Imido)vanadium(V) Complexes—Al Cocatalyst Systems

Abstract

Solution V K-edge XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure) analysis of vanadium(V) complexes containing both imido ligands and anionic ancillary donor ligands (L) of type, V(NR)(L)X2 (R = Ar, Ad (1-adamantyl); Ar = 2,6-Me2C6H3; X = Cl, Me, L = 2-(ArNCH2)C5H4N, OAr, WCA-NHC, and 2-(2’-benzimidazolyl)pyridine; WCA-NHC = anionic NHCs containing weak coordinating B(C6F5)3), which catalyze ethylene dimerization and/or polymerization in the presence of Al cocatalysts, has been explored. Different catalytically actives species with different oxidation states were formed depending upon the Al cocatalyst (MAO, Me2AlCl, AliBu3, etc.) and the anionic ancillary donor ligand employed. The method is useful for obtainment of the direct information of the active species (oxidation state, basic framework around the centered metal) in solution, and for better understanding in catalysis mechanism and organometallic as well as coordination chemistry.

Dissolving Vanadium into Titanium Nitride Lattice Framework for Rational Polysulfide Regulation in Li–S Batteries

“…The pre‐edge peak stands for the transition of V 1s electron to hybridized 3d orbital, which is a strong indicator of local structure symmetry. [ 34 ] The 1s to 3d transition is formally forbidden, it is possible when there is distortion in V symmetry and orbital mixing (V 3d mixed with np characters of N ligand in this case). The result depicts an intensifying pre‐edge peak till TVN‐4 upon the V dissolution, signifying the decreased VN 6 octahedral symmetry compared with that in perfect VN.…”

Recent progress on NHC-stabilized early transition metal (group 3–7) complexes: Synthesis and applications

“…Further characterization of these reactions by X-ray absorption spectroscopy (XAS) have been carried out to elucidate the oxidation state of the active species. 63,64 Norbornene and ethylene/norbornene copolymerization were also investigated with catalysts 74-76. 65 Scheme 25.…”

Enhanced Photodegradation in Metal Oxide Nanowires with Co-Doped Surfaces under a Low Magnetic Field

“…Complementary Co K-edge XANES measurements were taken during PD to determine the role of Co 2+ -rich doping in improved PD activity. 17,22 Figure 3a illustrates the Co K-edge XANES spectra of Co 2+ /ZnO NWs exposed to UV irradiation for various periods during PD, the spectra of which differed slightly depending on UV irradiation duration. In general, the valence states of the element can be quantified according to the half-height energy on the XANES edge.…”

“…The efficiency of PD activity is sensitive to changes in electronic structure. Complementary Co K-edge XANES measurements were taken during PD to determine the role of Co 2+ -rich doping in improved PD activity. , Figure a illustrates the Co K-edge XANES spectra of Co 2+ /ZnO NWs exposed to UV irradiation for various periods during PD, the spectra of which differed slightly depending on UV irradiation duration. In general, the valence states of the element can be quantified according to the half-height energy on the XANES edge. , The inset demonstrates that the half-height energy on the Co K-edge XANES shifted as UV irradiation duration increased, indicating that the energy level of the Co doping was near the Fermi level of the ZnO NWs; therefore, electrons could transfer from the Co 2+ /ZnO NWs to the MB solution and participate in PD as a function of UV irradiation duration .…”