B–B vs. B–H Bond Activation in a (μ-Hydrido)diborane(4) Anion upon Cycloaddition with CO2, Isocyanates, or Carbodiimides

  • The intriguing (μ-hydrido)diboranes(4) with their prominent pristine representative [B2H5]− have mainly been studied theoretically. We now describe the behavior of the planarized tetraaryl (μ-hydrido)diborane(4) anion [1H]− in cycloaddition reactions with the homologous series of heterocumulenes CO2, iPrNCO, and iPrNCNiPr. We show that a C=O bond of CO2 selectively activates the B−B bond of [1H]−, while the μ-H ligand is left untouched ([2H]−). The carbodiimide iPrNCNiPr, in contrast, neglects the B−B bond and rather adds the B-bonded H− ion to its central C atom to generate a formamidinate bridge across the B2 pair ([3]−). As a hybrid, the isocyanate iPrNCO combines the reactivity patterns of both its congeners and gives two products: one of them ([4H]−) is related to [2H]−, the other ([5]−) is an analog of [3]−. We finally propose a mechanistic scenario that rationalizes the individual reaction outcomes and combines them to a coherent picture of B–B vs. B–H bond activation.
Author:Timo TrageserGND, Dariusz Bebej, Michael BolteORCiD, Hans-Wolfram LernerGND, Matthias Wagner
Parent Title (German):Angewandte Chemie
Place of publication:Weinheim
Document Type:Article
Date of Publication (online):2021/03/19
Date of first Publication:2021/03/19
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2022/03/16
Tag:B−B bonds; B−H bonds; bond activation; cycloaddition; diboranes
Page Number:7
First Page:13500
Last Page:13506
T.T. thanks the Fonds der Chemischen Industrie for a Ph.D. grant. Open access funding enabled and organized by Projekt DEAL.
Institutes:Biochemie, Chemie und Pharmazie
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 54 Chemie / 540 Chemie und zugeordnete Wissenschaften
Licence (German):License LogoCreative Commons - Namensnennung-Nicht kommerziell - Keine Bearbeitung 4.0