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. 2021 Apr 6;60(15):8532-8536.
doi: 10.1002/anie.202101054. Epub 2021 Mar 4.

Reactions of B2 (o-tolyl)4 with Boranes: Assembly of the Pentaborane(9), HB[B(o-tolyl)(μ-H)]4

Karlee L Bamford  1 , Zheng-Wang Qu  2 , Douglas W Stephan  1
Affiliations

Reactions of B2 (o-tolyl)4 with Boranes: Assembly of the Pentaborane(9), HB[B(o-tolyl)(μ-H)]4

Karlee L Bamford et al. Angew Chem Int Ed Engl. .

Abstract

Reactions of the diborane(4) B2 (o-tolyl)4 and monohydridoboranes are shown to give B(o-tolyl)3 and (o-tolyl)BR2 (R2 =(C8 H14 ) 3, cat 4, pin 5, (C6 F5 )2 6) as the major products. The corresponding reaction with BH3 -sources gives complex mixtures, resulting from hydride/aryl exchange, dimerization and borane elimination. This led to the isolation of the first tetra-substituted pentaborane(9) HB[B(o-tolyl)(μ-H)]4 8. The reaction pathways are probed experimentally and by computations.

Keywords: boron; cluster; diborane(4); metathesis; pentaborane(9).

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
a) Known tetraaryl‐substituted diboranes(4), and b) hydrido‐substituted aryldiboranes(4).
Figure 2
Figure 2
POV‐ray depiction of a) 2, b) 4. B: yellow‐green; C: black; O: red. All hydrogen atoms have been omitted for clarity.
Scheme 1
Scheme 1
Reactions of 1 with hydridoboranes.
Figure 3
Figure 3
POV‐ray depiction of 8 as viewed from a) side‐on, and b) top‐down. B: yellow‐green, C: dark grey, H: light grey. All hydrogen atoms except those bound to boron centers have been omitted for clarity.
Scheme 2
Scheme 2
DFT‐computed free energy paths (in kcal mol−1, at 298 K temperature and 1 M concentration) for the reactions of 1 (Ar=o‐tolyl) in toluene with HBcat.
See this image and copyright information in PMC

References

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