Density Functional Study of 8‐ and 11‐Vertex Polyhedral Borane Structures: Comparison with Bare Germanium Clusters.

Abstract

Density functional theory (DFT) at the hybrid B3LYP level has been applied to the polyhedral boranes BnHnz (n = 8 and 11, z = −2, −4, and −6) for comparison with isoelectronic germanium clusters Genz. The energy differences between the global minima and other higher energy borane structures are much larger relative to the case of the corresponding bare germanium clusters. Furthermore, for both B8H82- and B11H112-, the lowest energy computed structures are the corresponding experimentally observed most spherical deltahedra predicted by the Wade−Mingos rules, namely the D2d bisdisphenoid and the C2v edge-coalesced icosahedron, respectively. Only in the case of B8H82- is there a second structure close (+2.6 kcal/mol) to the D2d bisdisphenoid global minimum, namely the C2v bicapped trigonal prism corresponding to the “square” intermediate in a single diamond−square−diamond process that can lead to the experimentally observed room temperature fluxionality of B8H82-. Stable borane structures with 3-fold symmetr...