Cooperative catalysts offer unique route to alkenes

December 11, 2015

Chemists at Princeton have developed a new chemical method to introduce valuable alkenes into simple hydrocarbon molecules, a transformation known as dehydrogenation, which is found in important processes such as the biosynthesis of essential fatty acids in the body and the commercial production of detergents.

Leading approaches in the natural and synthetic classes of reactions possess attractive features that are unavailable to the other. Existing synthetic methods produce hydrogen gas as a useful byproduct but require very high temperatures, while natural methods run at mild temperatures but produce a full equivalent of an unusable byproduct.

"What if we could have a method that offers the benefits of both approaches? Can we be greedy?" asked Julian West, a graduate student in the Sorensen lab and first author of the study published in Nature Communications. Guided by this goal, the researchers devised a novel two-component catalyst system that performs the dehydrogenation reaction at room temperature, making hydrogen gas and a molecule containing an alkene, or carbon-carbon double bond.

"If you're a chemist, you have a keen sense of the importance of the alkene," Erik Sorensen, the Arthur Allan Patchett Professor in Organic Chemistry at Princeton and corresponding author. Alkenes are highly versatile and can readily serve as starting materials in many reactions. "It's a portal to a whole range of compound types," he said.

The alkene was generated using a pair of catalysts to separately remove two hydrogen atoms from neighboring carbons atoms. To break the first, stronger carbon-hydrogen bond, the researchers chose a so-called hydrogen atom transfer catalyst known as decatungstate, which is activated by ultraviolet light. "We used light energy to get the reaction going," Sorensen said.

Once the first bond is broken, the adjacent hydrogen atom was much easier to remove using a second catalyst, a compound called cobaloxime. "It's like a one-two punch," West said, "once we had the substrate on the ropes, we didn't need a very strong catalyst to take the other hydrogen atom."

Another advantage of the method is that both catalysts are made of cheap, earth abundant metals, instead of the precious metals, such as iridium and rhodium, used in current state-of-the-art methods. However, the dual catalyst system has yet to reach the same level of efficiency as existing methods, which the researchers suspect is due to the alkene product binding to the decatungstate catalyst, inhibiting its participation in the reaction.

"The method is noted more for its conceptual uniqueness than its efficiency," Sorensen said.

It's the dual catalyst system design that could really "pay dividends," West said. The researchers plan to apply of their strategy to other chemical transformations as well. "We're all really excited because this reaction opens the door to catalysis for our group," he said.
-end-
Read the full article here:

West, J.G.; Huang, D.; Sorensen, E.J. "Acceptorless dehydrogenation of small molecules through cooperative base metal catalysis." Nature Commun. 2015, 6, 10093.

This work was supported by the National Institutes of Health General Medical Sciences (R01 GM065483), National Science Foundation (DGE 1148900) and Princeton University.

Princeton University

Related Catalyst Articles from Brightsurf:

Chemistry: How nitrogen is transferred by a catalyst
Catalysts with a metal-nitrogen bond can transfer nitrogen to organic molecules.

A 40-year-old catalyst unveils its secrets
Activity of the industrial catalyst TS-1 relies on titanium pairs / important discovery for catalyst development

Hydrochloric acid boosts catalyst activity
A research team from the Technical University of Munich (TUM) led by chemist Johannes Lercher has developed a synthesis process which drastically increases the activity of catalysts for the desulfurization of crude oil.

Scientists get atomistic picture of platinum catalyst degradation
Degradation of platinum, used as a key electrode material in the hydrogen economy, severely shortens the lifetime of electrochemical energy conversion devices, such as fuel cells.

Methanol synthesis: Insights into the structure of an enigmatic catalyst
To render the production process more efficient, it would be helpful to know more about the copper/zinc oxide/aluminium oxide catalyst deployed in methanol production.

Ultrastable, selective catalyst for propane dehydrogenation developed
A group of Japanese scientists has developed an ultrastable, selective catalyst to dehydrogenate propane - an essential process to produce the key petrochemical substance of propylene - without deactivation, even at temperatures of more than 600°C.

Asymmetric iodoesterification of simple alkenes by concerto catalyst
Japanese researchers have succeeded in catalytic asymmetric iodoesterification from simple alkene substrates and carboxylic acids.

Catalyst enables reactions with the help of green light
For the first time, chemists at the University of Bonn and Lehigh University in Bethlehem (USA) have developed a titanium catalyst that makes light usable for selective chemical reactions.

New catalyst provides boost to next-generation EV batteries
A recent study, affiliated with South Korea's Ulsan National Institute of Science and Technology (UNIST) has introduced a new composite catalyst that could efficiently enhance the charg-discharge performances when applied to metal-air batteries (MABs).

MOF co-catalyst allows selectivity of branched aldehydes of up to 90%
Heterogeneous catalysts are often preferred because of their robustness and lower operating costs, but homogenous catalysts still dominate when high selectivity is needed -- finding superior heterogeneous catalysts has been a challenge.

Read More: Catalyst News and Catalyst Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.