Related Experiment Video
Updated: Nov 12, 2025
Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy
Published on: November 9, 2019
B-B vs. B-H Bond Activation in a (μ-Hydrido)diborane(4) Anion upon Cycloaddition with CO2 , Isocyanates, or
Timo Trageser1, Dariusz Bebej1, Michael Bolte1
1Institut für Anorganische Chemie, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, 60438, Frankfurt (Main), Germany.
Abstract:
The intriguing (μ-hydrido)diboranes(4) with their prominent pristine representative [B2 H5 ]- 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.
More Related Videos
Related Concept Videos
03:08Hydroboration-Oxidation of Alkenes
01:16Cycloaddition Reactions: MO Requirements for Thermal Activation
02:36Regioselectivity and Stereochemistry of Hydroboration
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
01:17Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
![[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12417.jpg&w=3840&q=75)
01:16[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction