Synthesis and characterization of tetraphenylammonium salts

Making an ion that has defied synthesis

31 August 2022

The tetraphenylammonium ion — a nitrogen atom surrounded by four phenyl groups — has now been synthesised in the lab after defying all attempts to make it for more than a century.

The six elements boron, aluminium, carbon, silicon, nitrogen and phosphorus all tend to form bonds with four groups. When all four groups are phenyl — essentially the molecule benzene minus a hydrogen atom — these elements form tetraphenyls, which have a windmill-like structure with four phenyl arms radiating from the element in the centre. These molecules and ions have been synthesised between 1885 and 1950 — with the exception of that of nitrogen (tetraphenylammonium), leading to speculation that it can’t be synthesised.

Now, five researchers at Kanazawa University in Japan have succeeded in making tetraphenylammonium for the first time by adopting a synthesis method known as radical coupling.

The development of large-scale ways to make the ion could see it used in various areas of research in the future.

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References

1. Nature Communications 13, 2537 (2022). doi: 10.1038/s41467-022-30282-y