Modern computational protocols based on the density functional theory (DFT) infer that polyhedral closo ten-vertex carboranes are key starting stationary states in obtaining ten-vertex cationic carboranes. The rearrangement of the bicapped square polyhedra into decaborane-like shapes with open hexagons in boat conformations is caused by attacks of N-heterocyclic carbenes (NHCs) on the closo motifs. Single-point computations on the stationary points found during computational examinations of the reaction pathways have clearly shown that taking the "experimental" NHCs into account requires the use of dispersion correction. Further examination has revealed that for the purposes of the description of reaction pathways in their entirety, i.e., together with all transition states and intermediates, a simplified model of NHCs is sufficient. Many of such transition states resemble in their shapes those that dictate Z-rearrangement among various isomers of closo ten-vertex carboranes. Computational results are in very good agreement with the experimental findings obtained earlier.

Department of Chemistry and Biochemistry Auburn University Auburn AL 36849 USA

Faculty of Chemical Technology University of Pardubice CZ 532 10 Pardubice Czech Republic

Institute of Inorganic Chemistry of the Czech Academy of Sciences CZ 250 68 Husinec Řež Czech Republic

Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences CZ 166 10 Praha 6 Czech Republic

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