Stoy Andreas, Härterich Marcel, Dewhurst Rian D, Jiménez-Halla J Oscar C, Endres Peter, Eyßelein Maximilian, Kupfer Thomas, Deissenberger Andrea, Thiess Torsten, Braunschweig Holger
Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
J Am Chem Soc. 2022 Mar 2;144(8):3376-3380. doi: 10.1021/jacs.2c00479. Epub 2022 Feb 18.
Doubly N-heterocyclic-carbene-stabilized diborenes undergo facile reactions with CO, initially providing dibora-β-lactones. These lactones convert over time to their 2,4-diboraoxetan-3-one isomers through a presumed dissociative pathway and hypovalent boron species borylene carbonyls (LHB═C═O) and base-stabilized oxoboranes (LHB═O). Repeating these reactions with doubly cyclic(alkyl)(amino)carbene-stabilized diborenes allowed the isolation of a borylene carbonyl intermediate, whereas a base-stabilized oxoborane could be inferred by the isolation of a boroxine from the reaction mixture. These results, supported by calculations, confirm the presumed mechanism of the diboralactone-to-diboraoxetanone isomerization while also establishing a surprising level of stability for three unknown or very rare hypovalent boron species: base-stabilized derivatives of the parent borylene carbonyl (LHB═C═O) and parent oxoborane (LHB═O) as well as base-free oxoboranes (RB≡O).
双 N - 杂环卡宾稳定的二硼烯与 CO 容易发生反应，最初生成二硼 -β- 内酯。这些内酯会随着时间的推移通过推测的解离途径转化为它们的 2,4 - 二硼氧杂环丁烷 -3 - 酮异构体，同时生成低价硼物种硼烯羰基（LHB═C═O）和碱稳定的氧硼烷（LHB═O）。用双环（烷基）（氨基）卡宾稳定的二硼烯重复这些反应，可以分离出硼烯羰基中间体，而通过从反应混合物中分离出硼嗪可以推断出碱稳定的氧硼烷。这些结果在计算的支持下，证实了二硼内酯到二硼氧杂环丁烷酮异构化的推测机制，同时也为三种未知或非常罕见的低价硼物种建立了令人惊讶的稳定性水平：母体硼烯羰基（LHB═C═O）和母体氧硼烷（LHB═O）的碱稳定衍生物以及无碱氧硼烷（RB≡O）。
