Public Release: 

When Metal Meets Air: New Catalysts For Oxidizing Molecules May Result, UD Chemists Say

University of Delaware

SAN FRANCISCO, CA--By revealing exactly how oxygen and various organometallic molecules interact, fundamental studies at the University of Delaware may someday support the development of improved organometallic catalysts for making a variety of molecules--from plastics to hydrocarbon fuels, University of Delaware researchers reported April 15 during the American Chemical Society meeting.

Klaus H. Theopold, director of UD's Inorganic Synthesis Laboratory, is pairing chromium, a transition metal, with oxidizing agents capable of donating an oxygen atom to other molecules. The resulting organochromium molecules may ultimately result in more highly controlled catalytic production processes, including oxidation and polymerization reactions.

"We're seeing interesting changes in the reactivity of these molecules as we increase their oxidation level," Theopold explains. "That's of interest in olefin polymerization catalysis, for producing long-chain hydrocarbons including polyethylene [a plastic], and in oxidation catalysis, for making substances such as phenol from benzene [a fuel]."

To better understand the catalysts used in industrial oxidation processes, Theopold's research team is studying the reactions of dioxygen. Though it is "a strong oxidizer," Theopold notes, "dioxygen is not very reactive by itself--which explains why all these organic materials sitting around don't spontaneously burst into flames." Once dioxygen gets going, however, it will quickly incinerate every molecule in its path.

Theopold says he hopes his fundamental experiments may suggest a way to start oxidation catalysis reactions, control them and then stop them at specific points to obtain different products. Dioxygen undergoes some surprising reactions with chromium, he notes. For example, a chromium-phenol complex produces an intermediate product before yielding chromium oxo phenoxide--a precursor related to a phenol. "This represents the better part of the conversion of benzene to phenol," Theopold says.

Already, Theopold's colleague, Associate Chemistry Prof. Douglas J. Doren, has completed computer-based calculations that describe an intriquing dioxygen/cobalt complex. The complex uses two cobalt atoms, bound in a tris(pyrazolyl)borate ligand, to break dioxygen's strong oxygen/oxygen bond, thereby making oxygen available for further reactions. Though Doren's initial dioxygen/cobalt complex is too costly for larger-scale industrial applications, he says he hopes similar substances can be refined for catalyzing the oxidation of hydrocarbons.

Because the complex is "a relatively large, complex molecule" with 36 heavy atoms, Doren relies on UD's extensive computing resources--including a Cray J-90 system and Silicon Graphics multiprocessing computers, provided by the University and the National Science Foundation.

CONTACT:

Ginger Pinholster / Beth Thomas
University of Delaware
(302) 831-6408 or (302) 831-2791
(302) 435-6733 - Media Beeper
* During the meeting, call Ginger at (415) 394-1111 or send e-mail to ginger.pinholster@mvs.udel.edu

ACS presentation information - Theopold:
Moscone Center, Room 103, Exhibit Level
Tuesday, April 15, 2:50 p.m. (Pacific Time)

ACS presentation information - Doren:
San Francisco Hilton, Continental 8, Ballroom Level
Wednesday, April 16, 12:20 p.m. (PT)

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