Vibrational Spectrum and Electronic Structure of the [B₁₁H₁₁]^2– Dianion

Abstract

Abstract The vibrational spectrum, geometrical structure and electron‐density distribution (EDD) of the formally closo (2 n +2)‐electron cluster species [B 11 H 11 ] 2– have been studied. The presence of two low‐frequency vibrational modes is evidence of cluster nonrigidity. A rationale for this lies in the results of EDD calculations which show that the polyhedron lacks two‐centre edge‐localized B–B bonds of the 6 k –5 k type and that its surface exhibits two six‐membered rings with low electron density. Thus, the polyhedron does not consist of deltahedral faces only and therefore does not have a genuine closo structure. The data obtained also allow further elucidation of the “diamond‐square‐diamond” mechanism as commonly applied to the fluxionality of [B 11 H 11 ] 2– in solution.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)