Experimental and theoretical study of the vibrational spectrum, structure and electron density distribution of neutral 11-vertex dicarbaborane 2,3-C2B9H11

The presence of low-frequency large-amplitude modes in the vibrational spectrum, experimental and computed data on interboron distances and the results of the topological analysis of the electron density distribution in 2,3-C2B9H11, the molecule of a neutral 11-vertex dicarbaborane, lead to the conclusion that this polyhedron is not a deltahedron. This species lacks at least four two-center B-B bonds and thus it is formed not by triangular faces only. Hence, this dicarbaborane, as well as monocarbaborate [2-CB10H11]−, another representative of 11-vertex polyhedra, do not have the closo-structure, traditionally ascribed to both by formal [2n+2]-electron count.