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Issue 16, 2015
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Dimetallaborane analogues of pentaborane

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The structures of five-vertex dimetallaboranes Cp2M2B3H7 (Cp = η5-C5H5) of the second and third row transition metals, including the experimentally known Cp*2Rh2B3H7 (Cp* = η5-Me5C5), have been investigated by density functional theory. The predicted low-energy structures for Cp2M2B3H7 (M = Rh, Ir) are tetragonal pyramids similar to Cp*2Rh2B3H7 and pentaborane-9 B5H9 and consistent with their 14 Wadean skeletal electrons. Two Cp*2Rh2B3H7 structures with the same central Rh2B3 tetragonal prism are found with energies within ∼1 kcal mol−1 of each other, consistent with the experimental observation of two isomers in solution. The electron-richer Cp2M2B3H7 (M = Pd, Pt) systems having 16 Wadean skeletal electrons are predicted to exhibit more open structures analogous to the known structure for the valence isoelectronic pentaborane-11 B5H11. Trigonal bipyramids with the metal atoms at equatorial vertices are typically found to be low-energy structures for the hypoelectronic Cp2M2B3H7 systems (M = Ru, Os, Re, Mo, W, Ta). In addition, the low-energy Cp2Re2B3H7 structures of the rhenium derivatives Cp2Re2B3H7 provide examples of structures based on a central Re2B2 tetrahedron with the Re–Re edge bridged by the third boron atom. Such structures can be derived from a trigonal bipyramid by the rupture of one of the axial–equatorial edges.

Graphical abstract: Dimetallaborane analogues of pentaborane

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The article was received on 12 Jan 2015, accepted on 05 Mar 2015 and first published on 05 Mar 2015

Article type: Paper
DOI: 10.1039/C5DT00143A
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Dalton Trans., 2015,44, 7355-7363

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    Dimetallaborane analogues of pentaborane

    A. M. V. Brânzanic, A. Lupan and R. B. King, Dalton Trans., 2015, 44, 7355
    DOI: 10.1039/C5DT00143A

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