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Issue 36, 2012
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Untethered 4,1,2-MC2B10 supraicosahedral metallacarboranes, their C,C′-dimethyl 4,1,6-, 4,1,8- and 4,1,12-MC2B10 analogues, and DFT study of the (4,)1,2- to (4,)1,6-isomerisations of C2B11 carboranes and MC2B10 metallacarboranes

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Abstract

Reduction of the tethered carborane 1,2-μ-(CH2SiMe2CH2)-1,2-closo-C2B10H10 followed by metallation with {CpCo} or {(p-cymene)Ru} fragments affords both C,C′-dimethyl 4,1,2-MC2B10 and 4,1,6-MC2B10 species. DFT calculations indicate that the barriers to isomerisation of both 4-Cp-4,1,2-closo-CoC2B10H12 and 4-(η-C6H6)-4,1,2-closo-RuC2B10H12 to their respective 4,1,6-isomers are too high for this to be the origin of the unexpected formation of 4,1,6-MC2B10 products (in marked contrast to the related isomerisation of 1,2-closo-C2B11H13 to 1,6-closo-C2B11H13), and, indeed, the 4,1,2-species are recovered unchanged from refluxing toluene. Equally, the DFT-calculated profile for the isomerisation of [7,8-nido-C2B10H12]2− to [7,9-nido-C2B10H12]2− suggests that the unexpected formation of 4,1,6-metallacarboranes is unlikely to result from isomerisation of a reduced (nido) carborane following desilylation. Instead, the source of the 4,1,6-MC2B10 compounds is traced to desilylation of 1,2-μ-(CH2SiMe2CH2)-1,2-closo-C2B10H10 by Li or Na prior to reduction. The supraicosahedral metallacarboranes 1,8-Me2-4-Cp-4,1,8-closo-CoC2B10H10, 1,12-Me2-4-Cp-4,1,12-closo-CoC2B10H10 and 1,12-Me2-4-(p-cymene)-4,1,12-closo-RuC2B10H10 are also reported with all new species characterised both spectroscopically and crystallographically.

Graphical abstract: Untethered 4,1,2-MC2B10 supraicosahedral metallacarboranes, their C,C′-dimethyl 4,1,6-, 4,1,8- and 4,1,12-MC2B10 analogues, and DFT study of the (4,)1,2- to (4,)1,6-isomerisations of C2B11 carboranes and MC2B10 metallacarboranes

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Publication details

The article was received on 14 Jun 2012, accepted on 13 Jul 2012 and first published on 16 Jul 2012


Article type: Paper
DOI: 10.1039/C2DT31283B
Citation: Dalton Trans., 2012,41, 10957-10969
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    Untethered 4,1,2-MC2B10 supraicosahedral metallacarboranes, their C,C′-dimethyl 4,1,6-, 4,1,8- and 4,1,12-MC2B10 analogues, and DFT study of the (4,)1,2- to (4,)1,6-isomerisations of C2B11 carboranes and MC2B10 metallacarboranes

    A. McAnaw, M. Elena Lopez, G. Scott, D. Ellis, D. McKay, G. M. Rosair and A. J. Welch, Dalton Trans., 2012, 41, 10957
    DOI: 10.1039/C2DT31283B

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