Rearrangements in icosahedral boranes and carboranes revisited

Abstract

The structure, stability, and intermolecular rearrangements between ortho-, meta-, and para-C 2 B 10 H 12 and B 12 H 12 2À were investigated using the hybrid density functional B3LYP/6-31G(d) for vibrational frequencies, as well as B3LYP/6-311+G(2d,p) for single-point electronic energies. The general trends in free energies of rearrangement between ortho-C2B10H12 to meta-C2B10H12 and meta-C2B10H12 to para-C2B10H12 presented here are consistent with experimental reaction temperatures. In addition, the majority of the rearrangements can be viewed in terms of concerted diamond-square-diamond steps and triangular face rotations.

Enhancement of Luminescence Efficiencies by Thermal Rearrangement from ortho‐ to meta‐Carborane in Bis‐Carborane‐Substituted Acenes

“…It has been reported that some m ‐carborane derivatives have been generated by thermal rearrangements of o ‐carborane , . By heating above 425 °C, o ‐carborane was irreversibly transformed into the more stable m ‐carborane.…”

“…Since the discovery of o ‐carborane and its thermal rearrangement to m ‐carborane, many researchers have studied the mechanism of the transformation experimentally and theoretically , . Recently, computational analyses were performed by Brown and Mckee . Accordingly, it was proposed that the rearrangement proceeds by a triangular‐face rotation (TFR) process (Scheme ).…”

“…To investigate the rearrangement process theoretically, quantum chemical calculations were performed (Figure ). Transition‐state calculations were carried out according to the calculation procedure of Brown and McKee . Target species were optimized at the B3LYP/6‐31G(d) level of theory and frequency calculations were carried out at the same level to confirm whether they are stationary points.…”

Nine-vertex metallaborane chemistry. Preparation and characterisation of [1,1,1-(PMe3)2H-isocloso-IrB8H7-8-X], where X = H or Cl

“…3), effecting a classic diamondesquaree diamond rearrangement that is often postulated in borane, carborane and metallaborane chemistry [40,41]. This was simulated using relaxed potential energy surface scans, produced by squeezing the B(2)eB (4) Figures S1 and S2).…”

Thermochemistry of icosahedral closo-dicarboranes: a composite ab initio quantum-chemical perspective

“…closo-dicarboranes were the subject of extensive theoretical investigations. 8,9,10,11,12,13,14,15 However, there have been only a small number of correlated ab initio investigations of their thermochemical properties. Schleyer and Najafian (SN) calculated the relative stabilities of the para, meta, and ortho isomers at the MP2/6-31G(d) level of theory and found that the meta and ortho isomers lie 3.5 and 19.1 kcal mol -1 above the most stable para isomer.…”