If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.



Unusual Reaction ‘Decarbonizes’ An N-Heterocyclic Carbene

Carbene carbon gets displaced from its NHC scaffold yet remains linked to hafnium

by Stu Borman
April 6, 2015 | A version of this story appeared in Volume 93, Issue 14

Researchers have found an unusual transformation of an N-heterocyclic carbene (NHC) that could have implications for the design of new catalyst ligands. When NHCs act as ligands and form complexes with metals, the carbene carbon typically remains nonreactive. The carbene carbon has been known to react in some circumstances, and a group led by LeGrande M. Slaughter of Oklahoma State University, Stillwater, has found an extreme example of such a reaction (Chem. Commun. 2015, DOI: 10.1039/c5cc01560j). To carry out the reaction, Slaughter, now at the University of North Texas, and his team first converted a stable imidazolium cation to an imino-NHC intermediate. When the researchers added tetrabenzylhafnium, the intermediate was “decarbonized.” In this process, hafnium displaced the carbene carbon, but the latter didn’t flee the scene entirely. Instead, it jumped on hafnium’s back and hijacked three of hafnium’s benzyl groups (shown above). The reaction converted the neutral imino-NHC intermediate into a dianionic chelate ligand with three hafnium-linked nitrogens. The researchers demonstrated that the decarbonized chelate complex can catalyze ethylene polymerization. They now hope to find out whether similar rearrangements could play a role in activating other metal-based catalysts.

Chemical reaction of N-heterocyclic carbene.


This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.