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Immobilized Ti-calixarenes are active and selective catalysts

From C&E News Concentrates: December 6, 2004
Volume 82, Number 49
p. 33

Grafting titanium-calixarene complexes onto silica produces effective epoxidation catalysts, according to a study from the University of California, Berkeley. Chemical engineering professors Alexander Katz and Enrique Iglesia and graduate student Justin M. Notestein have shown that the immobilized form of the catalyst (shown) is more than 20 times more active and far more selective than the solution-phase compound in olefin epoxidation reactions using organic hydroperoxides as oxidizing agents [J. Am. Chem. Soc., published online Nov. 24, http://dx.doi.org/10.1021/ja0470259]. The researchers propose that the multidentate and bulky structure of the calixarene ligand keeps the metal centers isolated from one another during reaction with alkenes. Separating the titanium centers prevents oligomerization, which would lead to formation of unreactive and unselective Ti–O–Ti structures. The team notes that the catalysts are robust and reusable and exhibit long-term stability under ambient storage conditions.

Related sites:

Katz research site

Iglesia research site

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