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Multiple complexation of CO and related ligands to a main-group element


The ability of an atom or molecular fragment to bind multiple carbon monoxide (CO) molecules to form multicarbonyl adducts is a fundamental trait of transition metals. Transition-metal carbonyl complexes are vital to industry, appear naturally in the active sites of a number of enzymes (such as hydrogenases), are promising therapeutic agents1, and have even been observed in interstellar dust clouds2. Despite the wealth of established transition-metal multicarbonyl complexes3, no elements outside groups 4 to 12 of the periodic table have yet been shown to react directly with two or more CO units to form stable multicarbonyl adducts. Here we present the synthesis of a borylene dicarbonyl complex, the first multicarbonyl complex of a main-group element prepared using CO. The compound is additionally stable towards ambient air and moisture. The synthetic strategy used—liberation of a borylene ligand from a transition metal using donor ligands—is broadly applicable, leading to a number of unprecedented monovalent boron species with different Lewis basic groups. The similarity of these compounds to conventional transition-metal carbonyl complexes is demonstrated by photolytic liberation of CO and subsequent intramolecular carbon–carbon bond activation.

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Figure 1: Synthesis and reactivity of bis(CO), bis(isonitrile) and mixed adducts of boron.
Figure 2: Crystallographic and computational results on the molecules prepared herein.


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This work was supported by a European Research Council Advanced Grant to H.B.

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Authors and Affiliations



H.B. conceived and supervised the study. C.W.T., M.N. and Q.Y. performed the synthetic studies. F.H. and K.R. performed the single-crystal X-ray diffraction studies. A.V. performed the computational experiments. R.D.D. wrote the manuscript with input from all authors. All authors analysed the results and commented on the manuscript.

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Correspondence to Holger Braunschweig.

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The authors declare no competing financial interests.

Additional information

Crystallographic data have been deposited with the Cambridge Crystallographic Data Center as supplementary publication numbers CCDC 1049463–1049468. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre at

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Braunschweig, H., Dewhurst, R., Hupp, F. et al. Multiple complexation of CO and related ligands to a main-group element. Nature 522, 327–330 (2015).

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