Electronic structure of 10-vertex arachno-borane and -carborane clusters

AIM (Atoms in Molecules) analysis of electron density distribution based on the data of DFT B3LYP calculations was carried out for 10-vertex arachno-borane, -mono- and -dicarborane clusters ( [ arachno - B 10 H 14 ] 2 - , [ arachno - 6 - CB 9 H 14 ] - and arachno-6,9-C2B8H14). These 10-vertex arachno-compounds demonstrate discrepancy between geometry of the polyhedra and a number of skeleton electrons ascribed on the assumption of Wade/Williams rules. It was found that the calculated molecular graphs of the polyhedra studied differ notably from their traditional depictions, as not all edges of the polyhedra correspond to two-cener bonds. The endo-hydrogens of BH2 and CH2 groups and boron atoms of BH2 do not participate in the cage formation as was regarded earlier. Calculated IR spectra of the clusters investigated (frequency values, IR intensities and eigenvectors) agree well with their computed molecular graphs thus corroborating the proposed structures.