A Crystalline Boravinylidene from an Arrested Hydroboration Reaction

03 June 2025, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Boravinylidenes are postulated intermediates in 1,1-hydroboration and 1,1-carbaboration reactions of alkynes en route to vinyl boranes. Unlike transition metal-vinylidene complexes, boravinylidenes have hitherto, not been crystallographically characterized. Pairing 1,2-bis(trimethylsilyl)ethyne with an extremely potent hydroboration reagent, bis(1-methyl-ortho-carboranyl)borane, enabled crystallization and characterization of a previously speculated boravinylidene that features a vinyl cation with an adjacent borohydride. In solution, multinuclear NMR experiments validate the boravinylidene in equilibrium with the starting materials. Density functional theory calculations suggest the bulk of the bis(carboranyl)boryl unit and hyperconjugative interactions from the beta-silyl groups and the BH bond facilitate the stabilization of this unusual species. Reaction of the feature compound with nitriles triggered an insertion into one of the C–Si bonds and a hydride shift to furnish an iminium-tethered borataallene.

Supplementary materials

Title
Description
Actions
Title
Supporting Information
Description
Experimental details, NMR spectra, Computational details
Actions

Comments

Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.