1 research outputs found
Outer-Sphere Control of Catalysis on Surfaces: A Comparative Study of Ti(IV) Single-Sites Grafted on Amorphous versus Crystalline Silicates for Alkene Epoxidation
The effect of outer-sphere
environment on alkene epoxidation catalysis
using an organic hydroperoxide oxidant is demonstrated for calix[4]arene-Ti<sup>IV</sup> single-sites grafted on amorphous vs crystalline delaminated
zeotype (UCB-4) silicates as supports. A chelating calix[4]arene macrocyclic
ligand helps enforce a constant Ti<sup>IV</sup> inner-sphere, as characterized
by UV–visible and X-ray absorption spectroscopies, thus enabling
the rigorous comparison of outer-sphere environments across different
siliceous supports. These outer-sphere environments are characterized
by solid-state <sup>1</sup>H NMR spectroscopy to comprise proximally
organized silanols confined within 12 membered-ring cups in crystalline
UCB-4, and are responsible for up to 5-fold enhancements in rates
of epoxidation by Ti<sup>IV</sup> centers