Abstract
The design of larger architectures from smaller molecular building blocks by element–element coupling reactions is one of the key concerns of synthetic chemistry, so a number of strategies were developed for this bottom-up approach. A general scheme is the coupling of two elements with opposing polarity or that of two radicals. Here, we show that a B–B coupling reaction is possible between two boron analogues of the ethyl cation, resulting in the formation of an unprecedented dicationic tetraborane. The bonding properties in the rhomboid B4 core of the product can be described as two B–B units connected by three-centre, two-electron bonds, sharing the short diagonal. Our discovery might lead the way to the long sought-after boron chain polymers with a structure similar to the silicon chains in β-SiB3. Moreover, the reaction is a prime textbook example of the influence of multiple-centre bonding on reactivity.
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Acknowledgements
The authors thank W. Siebert for discussions and the Deutsche Forschungsgemeinschaft (DFG) for continuous financial support.
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H-J.H. conceived and supervised the study. S.L. performed the syntheses and the computational experiments. E.K. performed the X-ray crystallographic measurements. M.E. performed the DOSY-NMR measurements. S.L. and M.E. analysed the data and co-wrote the paper.
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Crystallographic data for compound 3[HB(C6F5)3]2. (CIF 69 kb)
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Litters, S., Kaifer, E., Enders, M. et al. A boron–boron coupling reaction between two ethyl cation analogues. Nature Chem 5, 1029–1034 (2013). https://doi.org/10.1038/nchem.1776
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DOI: https://doi.org/10.1038/nchem.1776
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