Jump to main content
Jump to site search

Issue 5, 2015
Previous Article Next Article

Isomerisation of nido-[C2B10H12]2− dianions: unprecedented rearrangements and new structural motifs in carborane cluster chemistry

Author affiliations

Abstract

Dianionic nido-[C2B10]2− species are key intermediates in the polyhedral expansion from 12- to 13-vertex carboranes and metallacarboranes, and the isomer adopted by these nido intermediates dictates the isomeric form of the 13-vertex product. Upon reduction and metallation of para-carborane up to five MC2B10 metallacarboranes can be produced (Angew. Chem., Int. Ed., 2007, 46, 6706), the structures of which imply the intermediacy of 1,7-, 3,7-, 4,7-, 7,9- and 7,10-isomers of the nido-[C2B10]2− species. In this paper we use density functional theory (DFT) calculations to characterise the reduction of closo-C2B10H12 carboranes and the subsequent isomerisations of the nido-[C2B10H12]2− dianions. Upon reduction para-carborane initially opens to [1,7-nido-C2B10H12]2− (abbreviated to 1,7) and [4,7-nido-C2B10H12]2− (4,7) and isomerisation pathways connecting 1,7 to 7,9, 4,7 to 7,10 and 1,7 to 3,7 have been characterised. For ortho- and meta-carborane the experimental reduction produces 7,9 in both cases and computed pathways for both processes are also defined; with ortho-carborane rearrangement occurs via7,8, whereas with meta-carborane 7,9 is formed directly. The 7,9 isomer is the global minimum nido-structure. The characterisation of these isomerisation processes uncovers intermediates that adopt new structural motifs that we term basket and inverted nido. Basket intermediates feature a two-vertex basket handle bridging the remaining 10 vertices; inverted nido intermediates are related to known nido species, in that they have 5- and 6-membered belts, but where the latter, rather than the former, is capped, leaving a 5-membered open face. These new intermediates exhibit similar stability to the nido species, which is attributed to their relation to the 13-vertex docosahedron through the removal of 5-connected vertices. Isomerisation pathways starting from nido geometries are most often initiated by destabilisation of the cluster through a DSD process causing the 3-connected C7 vertex to move into a 4-connected site and a neighbouring B vertex to become 3-connected. The ensuing rearrangement of the cluster involves processes such as the pivoting of a 4-vertex diamond about its long diagonal, the pivoting of two 3-vertex triangles about a shared vertex and DSD processes. These processes are all ultimately driven by the preference for carbon to occupy low-connected vertices on the open 6-membered face of the resulting nido species.

Graphical abstract: Isomerisation of nido-[C2B10H12]2− dianions: unprecedented rearrangements and new structural motifs in carborane cluster chemistry

Back to tab navigation

Supplementary files

Publication details

The article was received on 27 Feb 2015, accepted on 24 Mar 2015 and first published on 24 Mar 2015


Article type: Edge Article
DOI: 10.1039/C5SC00726G
Author version
available:
Download author version (PDF)
Citation: Chem. Sci., 2015,6, 3117-3128
  • Open access: Creative Commons BY license
  •   Request permissions

    Isomerisation of nido-[C2B10H12]2− dianions: unprecedented rearrangements and new structural motifs in carborane cluster chemistry

    D. McKay, S. A. Macgregor and A. J. Welch, Chem. Sci., 2015, 6, 3117
    DOI: 10.1039/C5SC00726G

    This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Material from this article can be used in other publications provided that the correct acknowledgement is given with the reproduced material.

    Reproduced material should be attributed as follows:

    • For reproduction of material from NJC:
      [Original citation] - Published by The Royal Society of Chemistry (RSC) on behalf of the Centre National de la Recherche Scientifique (CNRS) and the RSC.
    • For reproduction of material from PCCP:
      [Original citation] - Published by the PCCP Owner Societies.
    • For reproduction of material from PPS:
      [Original citation] - Published by The Royal Society of Chemistry (RSC) on behalf of the European Society for Photobiology, the European Photochemistry Association, and RSC.
    • For reproduction of material from all other RSC journals:
      [Original citation] - Published by The Royal Society of Chemistry.

    Information about reproducing material from RSC articles with different licences is available on our Permission Requests page.

Search articles by author

Spotlight

Advertisements