Group 4 Metallocenes Supported on Sulfated Zirconium Oxide Catalyze Benzene C–H Borylation

C–H bond functionalization of arenes with boranes continues to be a challenge in catalysis, with late transition and rare earth metals shown to be catalytically active. In this study, group 4 metallocenes grafted onto acidic sulfated zirconia (SZO) are demonstrated to catalyze arene borylation with pinacolborane (HBpin). Catalysis studies at partial HBpin conversions (59–68%) using Cp2M(Me)/SZO (M = Ti, Zr, or Hf; Cp = cyclopentadienyl) catalysts reveal that Zr exhibits greater selectivity and activity than Ti and Hf. At 0.16 mol % of Zr, Cp2ZrMe/SZO achieves 332 turnovers at high HBpin conversion (86%), making this catalyst comparably active to previously reported Ir and Rh C–H borylation catalysts. At 160 °C, a maximum chemoselectivity of 82% for PhBpin was observed at 24% HBpin conversion. The superior activity of ionic Cp2ZrMe/SZO compared to neutral Cp2ZrMe/SiO2 demonstrates the borylation mechanism relies on the highly electrophilic, coordinatively unsaturated cationic sites stabilized by the weakly coordinating sulfated support. Furthermore, both catalysts significantly outperform their molecular analogues, Cp2ZrMe2 and [Cp2ZrMe][B(C6F5)4], suggesting that the support enhances catalytic performance by stabilizing the active species.

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Regioselective Hydrosilylation Catalysis with Supported Well-Defined Pt(0) Complexes: Effects of Surface Anions and Phosphenium Ligands

Achieving stable, selective single-atom catalysts is challenging because localsurface-site structures are difficult to control. Surface organometallic chemistry and organic–inorganic hybrid materials ...

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Postdoctoral Research Associate - Ames National Laboratory

Position Title: Postdoctoral Research Associate - Ames National Laboratory Appointment Type: Post Doc/Trainee Job Description: Summary of Duties and Responsibilities: As a U. S. Department of Energy (...

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Determining the Conformation of Supported Complexes Using an 17O TEDOR-like NMR Experiment

Dynamic nuclear polarization surface-enhanced nuclear magnetic resonance (NMR) spectroscopy has enabled the determination of the three-dimensional configuration of surface sites, in particular supported metal complexes of relevance to single-site heterogeneous catalysis. These approaches have chiefly leveraged the application of NMR double-resonance experiments that either reveal the complex conformation via point-to-point intramolecular distances between spin-labeled atoms or the complex-surface orientation via distances between the spins and the surface plane. Either method typically requires expensive isotope labeling and each reports on different structural features. The application of an experiment that simultaneously reveals both types of distances with chemical resolution would be ideal. In this article, we describe an 17O{1H} pseudo-3D correlation experiment that achieves this goal. Specifically, Si–O–Si and Si–O–M oxygens are well-resolved by 17O NMR; therefore, distances can be simultaneously measured radially, between Si–17O–M and the 1H’s of the ligands, and vertically to the Si–17O–Si linkages of the silica support. We demonstrate the experiment using supported yttrium and zirconium complexes. Good agreement is obtained when comparing the experimental results to theoretical predictions from density functional theory calculations, highlighting the reliability of this relatively simple experiment.

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Research Scientist in Chemistry in Charlottesville, Virginia, United States of America | Research at University of Virginia

Apply for Research Scientist in Chemistry job with University of Virginia in Charlottesville, Virginia, United States of America. Research at University of Virginia

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Well-defined Pt(0) heterogeneous hydrosilylation catalysts supported by a surface bound phosphenium

Single atom, low valent transition metals are important for heterogeneous catalysis but are challenging to generate and stabilize in a well-defined manner. Herein, we explored the functionalization of...

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