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Can a Wanzlick-like equilibrium exist between dicoordinate borylenes and diborenes?

Fantuzzi, Felipe, Jiao, Yinchun, Dewhurst, Rian D., Weinhold, Frank, Braunschweig, Holger, Engels, Bernd (2022) Can a Wanzlick-like equilibrium exist between dicoordinate borylenes and diborenes? Chemical Science, 13 . pp. 5118-5129. ISSN 2041-6520. (doi:10.1039/D1SC05988B) (KAR id:96269)

Abstract

Boron chemistry has experienced tremendous progress in the last few decades, resulting in the isolation of a variety of compounds with remarkable electronic structures and properties. Some examples are the singly Lewis-base-stabilised borylenes, wherein boron has a formal oxidation state of +I, and their dimers featuring a boron–boron double bond, namely diborenes. However, no evidence of a Wanzlick-type equilibrium between borylenes and diborenes, which would open a valuable route to the latter compounds, has been found. In this work, we combine DFT, coupled-cluster, multireference methods, and natural bond orbital/natural resonance theory analyses to investigate the electronic, structural, and kinetic factors controlling the reactivity of the transient CAAC-stabilised cyanoborylene, which spontaneously cyclotetramerises into a butterfly-type, twelve-membered (BCN)4 ring, and the reasons why its dimerisation through the boron atoms is hampered. The computations are also extended to the NHC-stabilised borylene counterparts. We reveal that the borylene ground state multiplicity dictates the preference for self-stabilising cyclooligomerisation over boron–boron dimerisation. Our comparison between NHC- vs. CAAC-stabilised borylenes provides a convincing rationale for why the reduction of the former always gives diborenes while a range of other products is found for the latter. Our findings provide a theoretical background for the rational design of base-stabilised borylenes, which could pave the way for novel synthetic routes to diborenes or alternatively non-dimerising systems for small-molecule activation.

Item Type: Article
DOI/Identification number: 10.1039/D1SC05988B
Divisions: Divisions > Division of Natural Sciences > Chemistry and Forensics
Depositing User: Felipe Fantuzzi
Date Deposited: 17 Aug 2022 21:17 UTC
Last Modified: 18 Aug 2022 14:00 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/96269 (The current URI for this page, for reference purposes)

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