Silicon Nitride Surface Enabled Propane Dehydrogenation Catalyzed by Supported Organozirconium

Mesoporous silicon nitride (Si3N4) is a nontraditional
support for the chemisorption of organometallic complexes with the
potential for enhancing catalytic activity through features such as
the increased Lewis basicity of nitrogen for heterolytic bond activation,
increased ligand donor strength, and metal–ligand orbital overlap.
Here, tetrabenzyl zirconium (ZrBn4) was chemisorbed on
Si3N4, and the resulting supported organometallic
species was characterized by Diffuse Reflectance Infrared Fourier
Transform Spectroscopy (DRIFTS), Dynamic Nuclear Polarization-enhanced
Solid State Nuclear Magnetic Resonance (DNP-SSNMR), and X-ray Absorption
Spectroscopy (XAS). Based on the hypothesis that the nitride might
enable facile heterolytic C–H bond activation along the Zr–N
bond, this material was found to be a highly active (1.53 molpropene molZr–1 h–1 at 450 °C) and selective (99% to propylene) catalyst for propane
dehydrogenation. In contrast, the homologous silica supported complex
exhibited negligible activity under these conditions.