The Transition‐Metal‐Like Behavior of B2(NHC)2 in the Activation of CO: HOMO–LUMO Swap Without Photoinduction |
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| Authors: | Dr. Huaiyu Zhang Prof. Zexing Cao Prof. Wei Wu Prof. Yirong Mo |
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| Affiliation: | 1. Institute of Computational Quantum Chemistry, College of Chemistry and Material Science, Hebei Normal University, Shijiazhuang, China;2. Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry and State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, Xiamen, China;3. Department of Chemistry, Western Michigan University, Kalamazoo, USA |
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| Abstract: | It is a current trend to explore multi‐bonded and unsaturated main group compounds that can interact with small molecules, in order to find non‐metal catalysts. Notably, Braunschweig et al. found that diboryne stabilized by N‐heterocyclic carbenes (NHCs) can bind and activate CO. Here we explore the bonding nature of B2(NHC)2 and its activation mechanism for CO from a novel theoretical perspective. While the ground state of B2 is of a single bond, the approach of NHCs excites B2 to its third excited state of a triple bond with two significant σ‐holes at the two ends. The subsequent electrostatic attraction drives the formation of B2(NHC)2. However, only one of the two π bonds (HOMOs) of B2(NHC)2 fits to one of the degenerate LUMOs of CO. Interestingly, the strong steric repulsion between CO and B2(NHC)2 leads to the HOMO–LUMO swap in the latter. Subsequently, both HOMO and HOMO?1 of B2(NHC)2 can effectively interact with the two π* anti‐bonding orbitals (LUMO and LUMO+1) of CO, resulting in substantial electron back‐donation and the ultimate activation of CO. |
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| Keywords: | activation of CO diboryne Frontier orbitals valence bonds σ -Holes |
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