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Chemists subdue organolithiums by incorporating them into organogels

Air- and moisture-stable material makes these pyrophoric reagents safer and easier to handle

by Bethany Halford
February 27, 2023


A gloved hand holds a plug of material.
Credit: Nat. Chem.
Organolithium-loaded gels can be molded and handled in air.

Synthetic chemists prize organolithium reagents for their ability to build carbon-carbon bonds. But their extreme reactivity also makes them dangerous—they can spontaneously ignite when exposed to air or moisture. By incorporating organolithiums into an organogel, chemists at the University of York have rendered the reagents stable enough to handle in air, making them easier and safer to use.

While there are other ways to handle air- and moisture-sensitive organometallic reagents, including paraffin capsules and spring-loaded stir bars, the organolithium-loaded gels are easy to manufacture in bulk, says David K. Smith, who led the project with Peter O’Brien. “So if you’re a chemical supply company handling liters upon liters of this stuff, you can, in one go, convert all of it into a gel,” Smith says. The gel can then be sliced up into individual reagent doses.

To prepare the gels, the chemists mixed organolithium reagents, including phenyllithium, n-butyllithium, and s-butyllithium, with the alkane hexatriacontane (C36H74) using an inert atmosphere and warmed the solutions gently to dissolve the large alkane. They then cooled the solution—either in a flask or a syringe—until a gel formed. The gel could be used in the reaction flask in which it was made or extruded in portions from the syringe (Nat. Chem. 2023, DOI: 10.1038/s41557-023-01136-x).

The alkane assembles via noncovalent interactions into a nanostructured 3D network with the organolithium intercalated with its cavities. When using the gel as a reagent, a stir bar mechanically breaks it apart, releasing the organolithium. After the reaction, the gel’s large alkane can then be filtered out of the mixture. The gels maintained their reactive potency for up to 42 days when kept in sealed containers. The technique also works with organomagnesium halide reagents.

Eva Hevia, an expert in organometallic reagents at the University of Bern, says organolithiums are used widely in both academic and industrial labs around the world. “This work is a giant step forward towards changing the practice in the handling of polar organometallic reagents,” she says in an email. “I am very intrigued to see if these types of gels can also be prepared with other organometallic reagents such as organozinc or organoaluminium reagents which are also very sensitive to air and moisture and are also widely used in synthesis.”

Smith, who specializes in organic materials, and O’Brien, who specializes in organic synthesis, got the idea to use organogels to tame organolithiums about 10 years ago, after hearing Hevia give a talk about using deep eutectic solvents for easier handling of organolithiums.

Smith and O’Brien have been colleagues at York for more than 20 years, and they say the idea for the organolithium-loaded gels was born out of their collegiality. “If I hadn’t known Peter personally, I wouldn’t have put those things together,” Smith says.

O’Brien agrees. “To end up with a project that intersects our research interests that’s such a wacky, crazy idea, it’s probably one of the most rewarding things that I feel I’ve been part of here at York,” he says.

The chemists have patented the technology and are working with a commercial supplier. Next, they say, they’re interested in exploring materials that can release reagents on different time scales, asymmetric organolithium reagents, and organogels for other organometallics. “The periodic table is a big playground for all chemists,” Smith says.


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