Experimental assessment of the strengths of boron-boron triple bonds

Böhnke, Julian, Braunschweig, Holger, Constantinidis, Philipp, Dellermann, Theresa, Ewing, William C, Fischer, Ingo, Hammond, Kai, Hupp, Florian, Mies, Jan, Schmitt, Hans-Christian and Vargas, Alfredo (2015) Experimental assessment of the strengths of boron-boron triple bonds. Journal of the American Chemical Society, 137 (5). pp. 1766-1769. ISSN 1520-5126

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Abstract

Diborynes, molecules containing homoatomic boron-boron triple bonds, have been investigated by Raman spectroscopy in order to determine the stretching frequencies of their central B≡B unit as an experimental measure of homoatomic bond strength. The observed frequencies between 1600 cm-1 and 1750 cm-1 were assigned on the basis of DFT modelling and the characteristic pattern produced by the isotopic distribution of boron. This frequency completes the series of known stretches of homoatomic triple bonds, fitting into the trend established by the long-known stretching frequencies of C≡C and N≡N triple bonds in alkynes and dinitrogen, respectively. A quantitative analysis was carried out using the concept of relaxed force constants. The results support the classification of the diboryne as a true triple bond, and speak to the similarities of molecules constructed of the first-row elements of the p-block. The relaxed force constants of a recently reported diborabutatriene are also reported, which again fit into the trend established by the vibrational spectroscopy of organic cumulenes. As part of these studies, a new diboryne with decreased steric bulk was synthesized, and a computational study of the rotation of the stabilizing ligands indicated alkyne-like electronic isolation of the central B2-unit.

Item Type: Article
Schools and Departments: School of Life Sciences > Chemistry
Subjects: Q Science > QD Chemistry
Depositing User: Alfredo Vargas
Date Deposited: 22 Jan 2015 16:44
Last Modified: 26 May 2015 09:26
URI: http://sro.sussex.ac.uk/id/eprint/52141
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