Electronic Support Effects of Tunable Mixed Metal Oxides on Immobilized Palladium N‐Heterocyclic Carbene Complexes

Electronic effects of supports on site‐isolated organometallic complexes are poorly understood, despite indication that such effects impact stability and reactivity of immobilized complexes. Here we report X‐ray photoelectron spectroscopy (XPS) and X‐ray absorption near edge structure (XANES) spectr...

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Bibliographic Details
Published in:European journal of inorganic chemistry 2018-06, Vol.2018 (20-21), p.2471-2479
Main Authors: Finn, Matthew T., Donahue, Courtney M., Blake, Anastasia V., An, Nan, Daly, Scott R., Voutchkova‐Kostal, Adelina M.
Format: Article
Language:English
Subjects:
Aluminum
Carbene ligands
Electronegativity
Electronic properties
Electropositivity
Heterogeneous catalysis
Hydrotalcites
Image transmission
Inorganic chemistry
Iron
Magnesium
Metal oxides
Nickel
Palladium
Spectrum analysis
Stability
Support effects
Zinc
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Summary:Electronic effects of supports on site‐isolated organometallic complexes are poorly understood, despite indication that such effects impact stability and reactivity of immobilized complexes. Here we report X‐ray photoelectron spectroscopy (XPS) and X‐ray absorption near edge structure (XANES) spectroscopy studies of surface‐immobilized PdII N‐heterocyclic carbene complexes on Mg‐Al mixed metal oxides (MMOs) using silane‐modified ligands. XPS revealed a ca. 1 eV increase in Pd binding energy as a result of immobilization on MMOs, suggesting that the PdII complex becomes more electropositive when appended to the surface. For MMOs doped with Fe, Ni, Co and Zn, analysis of Cl K‐edge and Pd L2‐ and L3‐edge showed increasing pre‐edge energies that followed the order Fe = Ni < Zn = Cr < undoped Mg‐Al MMO. The Pd L3 pre‐edge energies correlated to the calculated oxygen partial charge of the MMO, as estimated using the Sanderson electronegativity model. Transmission electron microscope images collected on the immobilized Pd complexes revealed nanoparticles on three of the five MMOs, whose presence can be related to the Pd XPS and XANES energies. These findings suggest that electronic differences associated with the MMO supports impact the stability of appended PdII complexes with respect to reduction to Pd0. Here we report XPS and XANES spectroscopy studies of surface‐immobilized PdII N‐heterocyclic carbene complexes on Mg‐Al mixed metal oxides (MMOs) using silane‐modified ligands.
ISSN:1434-1948
1099-0682
DOI:10.1002/ejic.201800220