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Crystals 2017, 7(8), 234;

What Can We Learn from the Crystal Structures of Metallacarboranes?

Institute of Chemical Sciences, School of Engineering & Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK
Received: 26 June 2017 / Revised: 25 July 2017 / Accepted: 25 July 2017 / Published: 29 July 2017
(This article belongs to the Special Issue Crystal Structures of Boron Compounds)
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The determination of the molecular structures of metallacarboranes by X-ray diffraction remains critical to the development of the field, in some cases being the only viable way in which the overall architecture and the isomeric form of the molecule can be established. In such studies one problem frequently met is how to distinguish correctly {BH} and {CH} vertices, and this review begins by describing two relatively new methods, the Vertex-Centroid Distance (VCD) and Boron-Hydrogen Distance (BHD) methods, that have been developed to overcome the problem. Once the cage C atoms are located correctly, the resulting metallacarborane structure can frequently be analysed on the basis that cage B has a greater Structural Trans Effect (STE) than does cage C. In the absence of significant competing effects this gives rise to unequal M–L distances for a homogeneous ligand set and to a preferred Exopolyhedral Ligand Orientation (ELO) for a heterogeneous ligand set. ELO considerations can be used, amongst other things, to rank order the STEs of ligands and to identify suspect (in terms of cage C atom positions) metallacarborane structures. View Full-Text
Keywords: crystal structure; metallacarborane; structural trans effect; exopolyhedral ligand orientation crystal structure; metallacarborane; structural trans effect; exopolyhedral ligand orientation

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Welch, A.J. What Can We Learn from the Crystal Structures of Metallacarboranes? Crystals 2017, 7, 234.

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