In contrast to naturally occurring F2, O2 and N2, diatomic C2 is an intriguing species that has only been observed indirectly in the gas phase, and because of its high reactivity has eluded isolation in the condensed phase. It has previously been stabilized in L→C2←L compounds but the bonding situation of the central C2 in this motif differs remarkably from that of free C2. Here we have prepared and structurally characterized diatomic C2 as a monoligated complex L→C2 using a bulky phosphine ligand bearing two imidazolidin-2-iminato groups (L is (NHCR=N)2(CH3)P, where NHCR is an N-heterocyclic carbene). The compound is stable in solution at ambient temperature and has also been isolated in the solid state. Reactivity studies, in combination with quantum chemical analysis, suggest that the two carbon atoms of the L→C2 complex both have carbene character. The complex underwent intermolecular C–H bond activation upon thermolysis and exhibited hydroalkoxylation-like reactivity with methanol.
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Crystallographic data for the structures in this paper have been deposited at the Cambridge Crystallographic Data Centre under reference numbers 1993538 (2), 1993539 (6), 1993540 (4), 1993541 (3) and 1993542 (5). Copies of the data can be obtained free of charge from www.ccdc.cam.ac.uk/structures/. All other data supporting the findings of this study are available within the article and its Supplementary Information, or from the corresponding authors upon reasonable request.
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This research was supported in part by the Ministry of Science & Technology of Taiwan (108-2113-M-001-026-MY3), an Academia Sinica Investigator Award Grant (AS-IA-108-M04), the National Natural Science Foundation of China (grant numbers 21703099, 21973044 and 21828101), the Natural Science Foundation of Jiangsu Province for Youth (grant number BK20170964) and Nanjing Tech University (grant numbers 39837123 and 39837132). We are grateful to the High-Performance Computing Center of Nanjing Tech University for supporting the computational resources. T.Y. acknowledges financial support from the Alexander von Humboldt foundation. Further support came from the Deutsche Forschungsgemeinschaft.
The authors declare no competing interests.
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Leung, TF., Jiang, D., Wu, MC. et al. Isolable dicarbon stabilized by a single phosphine ligand. Nat. Chem. 13, 89–93 (2021). https://doi.org/10.1038/s41557-020-00579-w