The molecular structures of pentaborane(9) and pentaborane(11) in the gas phase as determined by electron diffraction

Thermochemistry of the Boranes

“…B 5 H 9 has C 4v symmetry, determined experimentally ͑x-ray diffraction, 143 electron diffraction, 144,145 and microwave spectroscopy 146,147 and supported by ab initio calculations. 110,148 ͒ The rotational constants were derived from the data compiled by Beaudet.…”

Topomerization of a Distorted Diamond‐Shaped Tetraborane(4) and Its Hydroboration to a closo‐Pentaborane(7) with a nido Structure

“…As a tetragonal pyramid, it has, however, a nido structure 11. 12 The distances between the boron atoms in the base (167.9 (H‐bridged) and 187.3 pm) are considerably different from the value of 181.1 pm in nido ‐B 5 H 9 13. Furthermore, remarkable NMR shifts are observed for 3 b : The apical boron atom ( δ =−13.6 ppm ) is strongly deshielded (compared to δ =−48.3 ppm for nido ‐B 5 H 9 , δ =−53.1 ppm for 2,3,4‐trimethylpentaborane(9)),14 as are the bridging hydrogen atoms ( δ =+2.34 compared to δ =−2.28 ppm in nido ‐B 5 H 9 ).…”

Dimetallaborane analogues of pentaborane

“…Two Cp* 2 Rh 2 B 3 H 7 structures with the same central Rh 2 B 3 tetragonal pyramid are found with energies within ∼1 kcal mol −1 of each other consistent with the experimental observation of two isomers in solution. The electronricher Cp 2 M 2 B 3 H 7 (M = Pd, Pt) systems with 16 Wadean skeletal electrons are predicted to exhibit more open structures analogous to the known structure 3 for the valence isoelectronic pentaborane-11, B 5 H 11 .…”

“…In addition, a less stable hydrogen-richer pentaborane-11, B 5 H 11 , was also obtained in the early boron hydride studies. 2,3 The B 5 H 9 structure has a central B 5 tetragonal pyramid whereas the central B 5 unit of the B 5 H 11 structure has been described 3 as an "open-sided tetragonal pyramid".…”