The structure of the neocarborane molecule

Structural Phase Transitions in closo-Dicarbadodecaboranes C2B10H12

“…The icosahedral carborane molecule C 2 B 10 H 12 ( closo -dicarbadodecaborane) is known to exist in three isomeric forms: 1,2-C 2 B 10 H 12 , 1,7-C 2 B 10 H 12 , and 1,12-C 2 B 10 H 12 called here ortho -carborane ( o -), meta -carborane ( m -), and para -carborane ( p -), respectively (Figure ). Their molecular structures in the gas phase have been determined from electron diffraction studies, − thus providing an associated electrical dipole moment of 4.09, 2.58, and 0 D for the o -, m -, and p -isomers, respectively, as calculated in our work. The determination of the molecular structures in the solid state has been complicated by the important molecule dynamics at room temperature ( rt ), and it was determined first for the o -isomer by “taming” the disorder by means of cocrystallization with hexamethylphosphoramide …”

Gas-phase electron diffraction studies of the icosahedral carbaboranes, ortho-, meta- and para-C2B10H12

“…1). The ortho-carbaborane derivatives have been most studied since they have been prepared from the commercially available materials, decaborane (14), B 10 H 14 , and alkynes, over the years. Derivatives of all three icosahedral carbaboranes by substitution of terminal hydrogen atoms at carbon or boron atoms 3 have potential applications in diverse areas including supramolecular chemistry, 4 medicine, 5 polymers, 6 agents for extraction of metal ions 7 and as ligands for metals.…”

“…In the 1960s, Vilkov et al determined the structures of ortho-and meta-carbaboranes by gas-phase electron diffraction (GED) and found the average C-C/C-B/B-B bond distances to be 1.76 (7) and 1.775(10) A ˚for ortho-and meta-carbaborane, respectively. 13,14 In 1971, Bohn and Bohn determined the structures of all three isomers by GED. 15 For para-carbaborane, all five unique bond lengths were determined using a D 5d symmetry model, giving a C-B bond distance of 1.710(11) A ˚, B2-B3 1.792 (7), B2-B7 1.772 (13), C-H 1.15 (9) and B-H 1.216(21) A ˚.…”

Microwave Spectra and Structures of 1,2-(ortho)- and 1,7-(meta)-Carborane, C2B10H12

“…The MW spectra of the parent ortho-and meta-carboranes (1,2-C 2 11 B 10 H 12 and 1,7-C 2 11 B 10 H 12 ) have been recorded and assigned for the first time, together with those of the four monosubstituted ( 10 B) isotopologues of each of 1,2-C 2 10 B 11 B 9 H 12 and 1,7-C 2 10 B 11 B 9 H 12 . These two compounds contain more atoms (24) than the vast majority of asymmetrical tops assigned thus far by MW spectroscopy. The MW spectra confirm that the structures of both of these molecules are slightly distorted icosahedrons with C 2v symmetry.…”

“…Carboranes, which are solids at room temperature, have relatively high sublimation pressures, and this has made it possible to investigate their gas-phase structures using the gas electron-diffraction (GED) method. In 1965−1969, Vilkov and co-workers − reported the gas-phase structures of these two compounds. A few years later, another GED study was reported by Bohn and Bohn, who succeeded in obtaining a full structure for gaseous 1,12-C 2 B 10 H 12 , which has only two different B−B bond lengths because of its D 5d symmetry.…”