The activation of abundant molecules such as hydrocarbons and atmospheric nitrogen (N2) remains a challenge because these molecules are often inert. The formation of carbon–nitrogen bonds from N2 typically has required reactive organic precursors that are incompatible with the reducing conditions that promote N2 reactivity1, which has prevented catalysis. Here we report a diketiminate-supported iron system that sequentially activates benzene and N2 to form aniline derivatives. The key to this coupling reaction is the partial silylation of a reduced iron–dinitrogen complex, followed by migration of a benzene-derived aryl group to the nitrogen. Further reduction releases N2-derived aniline, and the resulting iron species can re-enter the cyclic pathway. Specifically, we show that an easily prepared diketiminate iron bromide complex2 mediates the one-pot conversion of several petroleum-derived arenes into the corresponding silylated aniline derivatives, by using a mixture of sodium powder, crown ether, trimethylsilyl bromide and N2 as the nitrogen source. Numerous compounds along the cyclic pathway are isolated and crystallographically characterized, and their reactivity supports a mechanism for sequential hydrocarbon activation and N2 functionalization. This strategy couples nitrogen atoms from N2 with abundant hydrocarbons, and maps a route towards future catalytic systems.
It's "easily prepared", eh? Let's take a moment to appreciate the toxic, volatile, pyrophoric nature of this concoction:
"sodium powder, crown ether, trimethylsilyl bromide and N2"
Well, the N2 is probably fine.
The pyrophoric sodium powder might even be a good thing, because it will cause an inferno long before the crown ether has a chance to form explosive peroxides.
Yea, seriously. I love how nonchalant it sounded in the article, too. "They also treated the nitrogen with a silicon compound that allowed the nitrogen to combine with benzene."
I flinched when I got to "silicon" out of force of habit...
When it’s boiled to dryness, crown ether can produce peroxides that are unstable enough to explode on their own with shock or additional heat - no oxygen needed.
It’s a not-uncommon mistake to make in a synthetic lab.
My understanding is that evaporating solvent away doesn't form peroxides. Rather, as an ether ages, it can peroxidize. Removing the solvent concentrates the peroxides is all. Sure, it's a little tricky, but they're reporting results of chemistry research, which doesn't mean immediate real world application.
The activation of abundant molecules such as hydrocarbons and atmospheric nitrogen (N2) remains a challenge because these molecules are often inert. The formation of carbon–nitrogen bonds from N2 typically has required reactive organic precursors that are incompatible with the reducing conditions that promote N2 reactivity1, which has prevented catalysis. Here we report a diketiminate-supported iron system that sequentially activates benzene and N2 to form aniline derivatives. The key to this coupling reaction is the partial silylation of a reduced iron–dinitrogen complex, followed by migration of a benzene-derived aryl group to the nitrogen. Further reduction releases N2-derived aniline, and the resulting iron species can re-enter the cyclic pathway. Specifically, we show that an easily prepared diketiminate iron bromide complex2 mediates the one-pot conversion of several petroleum-derived arenes into the corresponding silylated aniline derivatives, by using a mixture of sodium powder, crown ether, trimethylsilyl bromide and N2 as the nitrogen source. Numerous compounds along the cyclic pathway are isolated and crystallographically characterized, and their reactivity supports a mechanism for sequential hydrocarbon activation and N2 functionalization. This strategy couples nitrogen atoms from N2 with abundant hydrocarbons, and maps a route towards future catalytic systems.