Surface structural-chemical characterization of a single-site d0 heterogeneous arene hydrogenation catalyst having 100% active sites

Linda A. Williams, Neng Guo, Alessandro Motta, Massimiliano Delferro, Ignazio L. Fragalà, Jeffrey T. Miller, Tobin J. Marks

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

Structural characterization of the catalytically significant sites on solid catalyst surfaces is frequently tenuous because their fraction, among all sites, typically is quite low. Here we report the combined application of solid-state 13C-cross-polarization magic angle spinning nuclear magnetic resonance (13C-CPMAS-NMR) spectroscopy, density functional theory (DFT), and Zr X-ray absorption spectroscopy (XAS) to characterize the adsorption products and surface chemistry of the precatalysts (η5-C5H5)2ZrR2 (R = H, CH3) and [η5-C5(CH3) 5]Zr(CH3)3 adsorbed on Brønsted superacidic sulfated alumina (AlS). The latter complex is exceptionally active for benzene hydrogenation, with ∼100% of the Zr sites catalytically significant as determined by kinetic poisoning experiments. The 13C-CPMAS-NMR, DFT, and XAS data indicate formation of organozirconium cations having a largely electrostatic [η5-C 5(CH3)5]Zr(CH3)2 +···AlS- interaction with greatly elongated Zr···OAlS distances of ∼2.35(2) Å. The catalytic benzene hydrogenation cycle is stepwise understandable by DFT, and proceeds via turnover-limiting H2 delivery to surface [η5-C5(CH3)5]ZrH 2(benzene)+···AlS- species, observable by solid-state NMR and XAS.

Original languageEnglish
Pages (from-to)413-418
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume110
Issue number2
DOIs
Publication statusPublished - Jan 8 2013

Keywords

  • DFT calculations
  • Organometallic chemistry
  • Solid acids
  • Surface catalysis

ASJC Scopus subject areas

  • General

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