Room-temperature chemical synthesis of C2

Kazunori Miyamoto,Masanobu Uchiyama,Mutsumi Kimura,Taisei Osawa,Masahito Ochiai,Shodai Narita,Yui Masumoto,Takahiro Hashishin

doi:10.1038/s41467-020-16025-x

Kazunori Miyamoto, Masanobu Uchiyama + Show 6 more

Open Access

https://doi.org/10.1038/s41467-020-16025-x

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Abstract

Diatomic carbon (C2) is historically an elusive chemical species. It has long been believed that the generation of C2 requires extremely high physical energy, such as an electric carbon arc or multiple photon excitation, and so it has been the general consensus that the inherent nature of C2 in the ground state is experimentally inaccessible. Here, we present the chemical synthesis of C2 from a hypervalent alkynyl-λ3-iodane in a flask at room temperature or below, providing experimental evidence to support theoretical predictions that C2 has a singlet biradical character with a quadruple bond, thus settling a long-standing controversy between experimental and theoretical chemists, and that C2 serves as a molecular element in the bottom-up chemical synthesis of nanocarbons such as graphite, carbon nanotubes, and C60.

Highlights

Diatomic carbon (C2) is historically an elusive chemical species
Theoretical/computational simulation has been applied recently, and the results indicated that C2 has a quadruple bond with a singlet biradical character in the ground state[13,14]
Exposure of 1a to 1.2 equivalents of tetra-n-butylammonium fluoride (Bu4NF) in dichloromethane resulted in smooth decomposition at −30 °C with the formation of acetylene and iodobenzene, indicating the generation of C2! all attempts to capture C2 with a range of ketones and olefins, such as acetone (3), 1,3,5,7-cyclooctatetraene (4), styrene (7), and 1,3,5-cycloheptatriene, failed, though they smoothly reacted with arc-generated C2 on an argon matrix at −196 °C3–5,20

Summary

C C I FBF3 Room

B Isolation of C2 stabilized by potent electron-donating ligands. c Our chemical synthesis of C2 at ambient temperature under normal pressure by utilizing hypervalent alkynyl-λ3-iodane 1a. B Isolation of C2 stabilized by potent electron-donating ligands. C Our chemical synthesis of C2 at ambient temperature under normal pressure by utilizing hypervalent alkynyl-λ3-iodane 1a. Experimental evidence that C2 may serve as a key intermediate in the formation of various carbon allotropes (Fig. 1c)

Results

FBF3 Ph

Methods