Boranes.  XLVI.  Nuclear magnetic resonance studies of octaborane(14) and isononaborane(15)

Moody, David C.; Schaeffer, Riley

doi:10.1021/ic50155a048

Cited by 22 publications

(7 citation statements)

References 5 publications

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“…However, the exact positions of the six extra hydrogens are not known. The experimental 11 B NMR spectrum is simple: three doublets, suggesting C 3 v symmetry (see 2 in Figure ). , Moody and Schaeffer redetermined the 1 H and 11 B NMR spectra and agreed with the earlier C 3 v proposal . However, they concede that the possible rapid exchange of three bridge and three terminal hydrogens (instead of six equivalent bridging H's in the C 3 v geometry) could not be excluded.…”

Section: Resultssupporting

confidence: 64%

“…However, they concede that the possible rapid exchange of three bridge and three terminal hydrogens (instead of six equivalent bridging H's in the C 3 v geometry) could not be excluded. In particular, it was questioned whether six hydrogen bridges could be accommodated on an open B 6 face, since this might be unfavorable sterically which also would be consistent with the experimental observation of only three 11 B signals with equal intensity.…”

Section: Resultsmentioning

confidence: 94%

“…Computed B−H μ distances are 1.255 and 1.474 Å for B4,6,8 and B5,7,9, respectively. Typical B−H μ distances are around 1.30−1.35 Å. Moody and Schaeffer deduced “a slight asymmetry of the bridges”, toward B4,6,8 and away from B5,7,9, from the observed large J 11 B - 1 H coupling of 50 Hz between B4,6,8 and bridging hydrogens . They also gave a rough estimate of 25−35 Hz for the B5,7,9-H μ coupling.…”

Section: Resultsmentioning

confidence: 99%

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Solid State and Solution Structures of 9-Vertex Arachno Boron Hydride Clusters. An ab Initio/IGLO/NMR Study

Hofmann

Schleyer

1999

Inorg. Chem.

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The ab initio/IGLO/NMR method clarifies the structures of several 9-vertex boron hydride clusters by comparing computed chemical shifts using various geometries with NMR data in solution. The experimental coordinates of n-B 9 H 15 give an energy 110 kcal mol -1 above the fully optimized ab initio geometry. The experimental boron positions were shown to be accurate, but not the hydrogen placements. n-B 9 H 15 , which has a 7-vertex open face binding five bridge hydrogens and one endo terminal H, is 2.2 kcal mol -1 lower in energy than the isomer, i-B 9 H 15 . i-B 9 H 15 has a C 3V symmetric structure in solution with six asymmetric hydrogen bridges on the open B 6 face of the 9-vertex arachno cluster. In contrast to the C s structure reported for the solid state, [B 9 H 14 ] -is shown to have a fluctional C 1 structure in solution with an additional hydrogen bridge. However, the C s and C 1 geometries are very similar and the barriers for endo hydrogen rearrangements are 2.4 kcal mol -1 or less. B 9 H 13 ‚NCCH 3 favors C 1 symmetry in solution in contrast to the reported C s solid-state structure which has one fewer hydrogen bridge. In contrast to the experimental solid-state structures, in solution B 9 H 13 ‚NCCH 3 and [B 9 H 14 ] -are isostructural. A solid-state model for [B 9 H 13 ] 2-based on the presence of only three instead of five possible structures is proposed. These three structures may also coexist in a fluctuating mixture in solution.

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Section: Resultssupporting

confidence: 64%

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

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Solid State and Solution Structures of 9-Vertex Arachno Boron Hydride Clusters. An ab Initio/IGLO/NMR Study

Hofmann

Schleyer

1999

Inorg. Chem.

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“…Comparison NMR data for the eight-vertex subcluster are very limited. Because of the symmetry, whether absolute or timeaveraged, 32 of the parent model arachno-B8H14, a comparison with its 11 B nuclear magnetic shielding pattern is not very informative. As discussed above, the arachno-octaborane subcluster of 3a is formally cationic.…”

Section: Cd2cl2mentioning

confidence: 99%

Substitution of the laser borane anti-B₁₈H₂₂ with pyridine: a structural and photophysical study of some unusually structured macropolyhedral boron hydrides

et al. 2018

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Reaction of anti-BH1 with pyridine in neutral solvents gives sparingly soluble BH-3',8'-Py3a as the major product (ca. 53%) and BH-6',9'-Py2 (ca. 15%) as the minor product, with small quantities of BH-8'-Py 4 (ca. 1%) also being formed. The three new compounds 2, 3a and 4 are characterized by single-crystal X-ray diffraction analyses and by multinuclear multiple-resonance NMR spectroscopy. Compound 2 is of ten-vertex nido:ten-vertex arachno two-atoms-in-common architecture, long postulated for a species with borons-only cluster constitution, but previously elusive. Compound 3a is of unprecedented ten-vertex nido:eight-vertex arachno two-atoms-in-common architecture. The single-crystal X-ray diffraction analysis for the picoline derivative BH(NCHMe)3b, similarly obtained, is also presented. BHPy 4 is also previously unreported but is of known ten-vertex nido:ten-vertex nido two-atoms-in-common architecture of anti configuration, but now with the pyridine ligand positioned differently to other reported examples of BHL compounds. Factors behind the remarkably low solubility of 3a and 3b are elucidated in terms of electrostatic potential (ESP) calculations, polarity, and van der Waals complementarities. In view of contemporary developing high interest in the fluorescent properties of macropolyhedral boron-containing species, a detailed assessment of the photophysical characteristics of 3a and 4 is also presented. In contrast to the thermochromic fluorescence of 2 (from 620 nm brick-red at room temperature to 585 nm yellow at 8 K, quantum yield 0.15), compound 3a is only weakly phosphorescent in the yellow region (590 nm, quantum yield 0.01), whereas compound 4 exhibits no luminescence. The far more photoactive nature of compound 2 is associated with S excited-state minima structures that differ from each other only by the relative rotational positions of the pyridine substituents on its disubstituted ten-vertex {arachno-BPy}-subcluster. The wavelength and relative intensity of fluorescence from these structures depends on the rotational positions of the pyridine ligands, which in turn are influenced by temperature and/or rotational inhibition in the solid-state.

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“…These differences originate from the different electronegativities of B and C. Pentalenediide is a stable anion which maintains its aromaticity when coordinated. On the other hand, calculations indicate that neither free B 8 H 14 nor B 8 H 14 2À is a stable species, assuming the planar structure made of two fused 5-fold rings of the ligand in Cp* 2 Ru 2 B 8 H 14 (in fact free B 8 H 14 is known [21] and has been computed [22], but has a completely different structure). It follows that changing the electron count results in different consequences in both types of complexes.…”

Section: Discussionmentioning

confidence: 99%

Bonding and electronic structure of Cp*2Ru2(B8H14), a metallaborane analogue of dinuclear pentalene complexes

Boucher¹,

Ghosh²,

Halet³

et al. 2012

Journal of Organometallic Chemistry

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Boranes. XLVI. Nuclear magnetic resonance studies of octaborane(14) and isononaborane(15)

Cited by 22 publications

References 5 publications

Solid State and Solution Structures of 9-Vertex Arachno Boron Hydride Clusters. An ab Initio/IGLO/NMR Study

Solid State and Solution Structures of 9-Vertex Arachno Boron Hydride Clusters. An ab Initio/IGLO/NMR Study

Substitution of the laser borane anti-B₁₈H₂₂ with pyridine: a structural and photophysical study of some unusually structured macropolyhedral boron hydrides

Bonding and electronic structure of Cp*2Ru2(B8H14), a metallaborane analogue of dinuclear pentalene complexes

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Boranes. XLVI. Nuclear magnetic resonance studies of octaborane(14) and isononaborane(15)

Cited by 22 publications

References 5 publications

Solid State and Solution Structures of 9-Vertex Arachno Boron Hydride Clusters. An ab Initio/IGLO/NMR Study

Solid State and Solution Structures of 9-Vertex Arachno Boron Hydride Clusters. An ab Initio/IGLO/NMR Study

Substitution of the laser borane anti-B18H22 with pyridine: a structural and photophysical study of some unusually structured macropolyhedral boron hydrides

Bonding and electronic structure of Cp*2Ru2(B8H14), a metallaborane analogue of dinuclear pentalene complexes

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Substitution of the laser borane anti-B₁₈H₂₂ with pyridine: a structural and photophysical study of some unusually structured macropolyhedral boron hydrides