Structural Consequences of Electron Hyperdeficiency
Synthesis and crystal structure of an iron-cobalt metallocarborane having two closed polyhedra fused along an edge
A metallocarborane of novel structure, (CH3)4C4B8H 8FeCo(η5-C5H5), has been synthesized and structurally characterized from 11B and 1H FT NMR, mass spectroscopic, infrared, and single-crystal x-ray diffraction data. The dark green crystals are monoclinic, space group P21, with two molecules per unit cell and a = 7.203 (4) Å, b = 14.77 (2) Å, c = 8.830 (2) Å, and β = 99.7 (1)° (ρcalcd = 1.38, ρobsd = 1.38 g cm-3). The structure was solved by the heavy-atom method and refined by full-matrix least-squares procedures to a final R value of 0.069 and Rw = 0.081 for the 1657 reflections for which Fo2 > 3σ(Fo)2. The molecule contains a direct iron-cobalt bond and consists of two pentagonal bipyramidal units fused at a common iron atom with an additional BH group capping triangular faces on both polyhedra simultaneously. The structure is explained in terms of a shortage of two electrons in the cage framework, relative to the normal requirement for polyhedral clusters, which causes one BH group to adopt a capping location. These results are discussed in relation to the known structures of two osmium carbonyls and a diiron metallocarborane.
W. M. Maxwell et al., "Structural Consequences of Electron Hyperdeficiency," Journal of the American Chemical Society, American Chemical Society (ACS), Jan 1976.
The definitive version is available at https://doi.org/10.1021/ja00428a017
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© 1976 American Chemical Society (ACS), All rights reserved.