This nitrene has staying power

Nitrenes—octet-defying molecules with a neutral nitrogen atom bonded to only one other substituent—are typically so reactive that their lifetimes are measured in nanoseconds. But now chemists have created a nitrene that lasts for 3 days. The molecule is likely to find use as a ligand for transition-metal complexes, much like carbenes did in the 1990s, say University of Bremen chemists Jens Beckmann and Emanuel Hupf, who led the work.

The new nitrene owes its long lifetime to its surrounding substituent: a scaffold known as M^SFluind, which was first reported in 2011 by Kohei Tamao of Kyoto University and colleagues. In recent years, chemists have used variations of M^SFluind to stabilize other fleeting intermediates, including a bismuthinidene and a stibinidene.

This bulky scaffold prevents the nitrene from reacting and provides electronic stabilization. “With this magic substituent, we’re basically building up a wall behind the nitrogen atom,” Beckmann says.

Beckmann and Hupf’s team crystallized the nitrene and studied it using X-ray crystallography. Because the molecule is a ground-state triplet, meaning it has two unpaired electrons, the researchers also used electron paramagnetic resonance spectroscopy and superconducting quantum interference device magnetometry to characterize it (Science 2024, DOI: 10.1126/science.adp4963).

Guy Bertrand, who studies octet-defying molecules at the University of California San Diego, says it’s impressive that the Bremen team was able to isolate the triplet nitrene. He says in an email that the work also shows that the “M^SFluind family of substituents will allow for the isolation of hitherto elusive species, not only in main group chemistry, but also in transition metal chemistry.”