Ab Initio Studies on Disubstituted closo‐Icosahedral Heteroboranes, X₂B₁₀H₁₀ [X = CH, SiH, N, P, and Sb]

Abstract

Ab initio theoretical studies on X2B10H10 (X = CH, SiH, N, P and Sb) have been done for all the three possible isomers. Unlike lower‐vertex heteroboranes, all the hetero derivatives have shown similar trends in the relative stabilities, the 1,12‐isomer being more stable followed by 1,7‐ and 1,2‐isomers, except for N and Sb. No conventional 1,2‐isomer for N could be found. Instead, a new nido isomer which is 18.1 kcal/mol higher in energy than the most stable isomer has been located. Any hetero group substitution to icosahedral R12H122− is found to be thermodynamically destabilizing. However, the Nucleus Independent Chemical Shift criterion shows that all compounds, except for 8, have similar aromaticity.

Phosphaborane chemistry. Syntheses and calculated molecular structures of mono- and di-chloro derivatives of 1,2-diphospha-closo-dodecaborane(10)

“…As already pointed out by Jemmis et al, 17 the presence of the two P vertices in 1a and 1b brings about a considerable distortion of the icosahedral [B 12 H 12 ] 2Ϫ skeleton. For instance, the B(3)-P(2)-B(6) and B(8)-P(7)-B (11) angles are reduced from ideal 108.0Њ to 93.0Њ and 93.5Њ, respectively, as calculated now at the RMP2(fc)/6-31G* level.…”

“…6,16 The molecular structure of 3a was also determined by single-crystal X-ray diffraction in order to compare the icosahedral distortion brought about by the Cl and P atoms in the solid state with the parameters computed for free 3a. Although the structures of the parent compounds 1a and 1b have already been computed at the SCF level (6-31G*), 17 their geometries were re-optimised at the same level as for 2 and 3 in order to get a consistent set of molecular structures of all species of types 1, 2, and 3. Moreover, the MP2 bond lengths computed for boron clusters proved to be superior to those calculated at the SCF level.…”

The electronic structure of 1,2-PCB10H11 molecular films: a precursor to a novel semiconductor

“…Although the total energy is probably better estimated using DFT, there are, however, serious defi ciencies in using ab initio DFT to model electronic structure of the closocarboranes. Ab initio molecular calculations have been undertaken for ortho-phosphacarborane (1,2-PCB 10 H 11 ) [40,42], but the electronic structure was not provided by the authors.…”

Condensed Two- and Three-Dimensional Aromatic Systems: A Theoretical Study on the Relative Stabilities of Isomers of CB19H16+, B20H15Cl, and B20H14Cl2 and Comparison to B12H10Cl22-, C6H4Cl2, C10H7Cl, and C10H6Cl2

“…This in turn goes to the most stable 1,12- isomer (para) above 615 °C . Theoretical studies at various levels have confirmed these experimental trends (Table ) 1 Relative Energies of Isomers of CB 19 H 16 + and C 2 B 10 H 12 compoundrelative energy (kcal/mol)compoundrelative energy (kcal/mol) 1-CB 19 H 16 + 0.00 1,12-C 2 B 10 H 12 0.00 2-CB 19 H 16 + 5.71 1,7-C 2 B 10 H 12 2.82 3-CB 19 H 16 + 16.01 1,2-C 2 B 10 H 12 18.70 4-CB 19 H 16 + 33.10 …”