Cationic closo‐carboranes 2. Do computed 11B and 13C NMR chemical shifts support their experimental availability?

Hnyk, Drahomı́r; Jayasree, Elambalassery G.

doi:10.1002/jcc.23176

Cited by 8 publications

(10 citation statements)

References 42 publications

(15 reference statements)

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“…Small clusters are known to be very sensitive to the inclusion of electron dynamic correlation when shielding tensors are being calculated. 45 The GIAO-MP2 calculations predict 11 B chemical shifts that compare well with experimental values. Table 3 compares computed and experimental 11 B chemical shifts for 1b-1d.…”

Section: Resultssupporting

confidence: 58%

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A computational analysis of the apparent nido vs. hypho conflict: are we dealing with six- or eight-vertex open-face diheteroboranes?

et al. 2015

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A series of computational studies have been undertaken to investigate the electronic structures and bonding schemes for six hetero-substituted borane cages, all of which have been presented in the literature as potential hypho structures. The six species are hypho-7,8-[C2B6H13](-) (1a), hypho-7,8-[CSB6H11](-) (1b), hypho-7,8-[S2B6H9](-) (1c), hypho-7,8-[NSB6H11] (1d), exo-7-Me-hypho-7,8-[NCB6H12] (1e), and endo-7-Me-hypho-7,8-[NCB6H12] (1f) and the so-called mno rule has been applied to each of them. As no structural data are known for the carbathia-, azathia-, and dithiahexaboranes, we have also applied the ab initio/GIAO/NMR structural tool for 1b-1d, with 1c having been prepared for this purpose. We conclude that an mno count of 10 means that 1a, 1b, 1d, 1e, and 1f should be termed pseudo-nido or pseudo-hypho. Only 1c can be considered to be correctly termed hypho-7,8-[S2B6H9](-).

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Section: Resultssupporting

confidence: 58%

“…45 The GIAO-MP2 calculations predict 11 B chemical shifts that compare well with experimental values. To be formally hypho, an mno value of 12 should be satisfied for 1a, 1b, 1d, 1e, and 1f.…”

Section: Resultssupporting

confidence: 56%

A computational analysis of the apparent nido vs. hypho conflict: are we dealing with six- or eight-vertex open-face diheteroboranes?

et al. 2015

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“…Several studies on correlation between theoretical determined charges of the 11 B species and their corresponding measured chemical shifts in (hetero)boranes already exist using not only the concepts of Mulliken charge 59,69 or natural population 69,97 but also the QTAIM 33 analysis applied here, showing that there is no clear general relationship. As shown in Figure 3, we do not find an overall relation between the determined q B and experimentally observed δ BTE as well.…”

Section: ■ Results and Discussionmentioning

confidence: 96%

GIAO versus GIPAW: Comparison of Methods To Calculate ¹¹B NMR Shifts of Icosahedral Closo-Heteroboranes toward Boron-Rich Borides

2020

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In this work, we perform first-principle density functional theory calculations with the Perdew−Burke−Ernzerhof (PBE) exchange correlation functional to compare the results of the gauge-including atomic orbital (GIAO) method with the gauge-including projector-augmented wave (GIPAW) approach for isotropic 11 B nuclear magnetic resonance shifts. GIPAW had been used successfully for the theoretical calculation of nuclear magnetic parameters of 11 B species in strong ionic solid-phase compounds such as borates but had been applied very rarely to structures where boron is mainly involved in complex covalent bonding situations, for example, in icosahedra of boron-rich borides. Thus, we investigate the accuracy of both well-known methods and reliability of the effective treatment of core electrons on a test set containing 16 experimentally known closo-(hetero)dodecaboranes. In general, we find very good agreement between GIAO and GIPAW when compared to experimental observations. However, accidental degeneracies of the shift values are better predicted by GIPAW. The optimized molecular geometries on the PBE level agree well with gaseous electron diffraction data and lead to theoretical isotropic chemical 11 B shifts with root-mean-square errors of 2.1 and 1.0 ppm depending on the used model of converting absolute shieldings to chemical shifts. The comparison with results from hybrid functionals (B3LYP, B3LYP-D2, and PBE0) shows a minor improvement in accuracy, which is in agreement with 13 C shifts of sp 3 -hybridized species. In order to prove the reliability of the conversion parameters obtained by PBE, we report the calculated 11 B shifts of 1,2-, 1,7-, and 1,12-PCB 10 H 11 with GIAO and GIPAW to our knowledge for the first time. Additionally, Bader's analysis is carried out on the converged electron density for all boron species within the molecular test set, yielding no simple direct relation between charge and isotropic shifts.

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“…For some cases the necessity of employing dynamic electron correlation in computing shielding tensor is obvious. 6 Evidently, the shielding constant of an individual boron nucleus within the cluster molecule is influenced by the interaction with the other boron atoms that are present. There were attempts to assess substitution NMR effects in various cluster compounds by means of regression analysis.…”

Section: ■ Introductionmentioning

confidence: 99%

“…The resulting minima are subsequently subject to magnetic properties calculations using IGLO- or GIAO-based methods in nonrelativistic or relativistic (e.g., ZORA) implementations. , The degree of agreement between the calculated and experimental δ( 11 B) serves as a criterion for the correctness of the cluster geometry in solution. For some cases the necessity of employing dynamic electron correlation in computing shielding tensor is obvious . Evidently, the shielding constant of an individual boron nucleus within the cluster molecule is influenced by the interaction with the other boron atoms that are present.…”

Section: Introductionmentioning

confidence: 99%

Nuclear Magnetic Shielding of Monoboranes: Calculation and Assessment of¹¹B NMR Chemical Shifts in Planar BX₃and in Tetrahedral [BX₄]⁻Systems

et al. 2017

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B NMR chemical shifts of tricoordinated BX and tetracoordinated BX compounds (X = H, CH, F, Cl, Br, I, OH, SH, NH, and CH═CH) were computed, and the shielding tensors were explored not only within the nonrelativistic GIAO approach but also by application of both relativistic ZORA computations including spin-orbit coupling as well as scalar nonrelativistic ZORA computations (BP86 level of density functional theory). The contributions of the spin-orbit coupling to the overall shieldings are decisive for X = Br and I in both series. No relationship was found between the 2p orbital occupancies or 1/ΔE (difference between LUMO and suitably occupied MO that can be coupled with LUMO) with the shielding tensors (or their principal values) in the BX series. However, a multidimensional statistical approach known as factor analysis (frequently used in chemometrics) revealed that three factors account for 92% of the cumulative proportion of total variance. The main components of the first factor are occupancies in the 2p and 2p orbitals and 1/ΔE; the second factor is mainly the occupancy in the 2p orbital and the inductive substituent parameters by Taft. Finally, the third factor consists exclusively (98.4%) of the electrostatic potential (V), which is directly related to the so-called π-hole magnitudes.

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Cationic closo‐carboranes 2. Do computed ¹¹B and ¹³C NMR chemical shifts support their experimental availability?

Cited by 8 publications

References 42 publications

A computational analysis of the apparent nido vs. hypho conflict: are we dealing with six- or eight-vertex open-face diheteroboranes?

A computational analysis of the apparent nido vs. hypho conflict: are we dealing with six- or eight-vertex open-face diheteroboranes?

GIAO versus GIPAW: Comparison of Methods To Calculate ¹¹B NMR Shifts of Icosahedral Closo-Heteroboranes toward Boron-Rich Borides

Nuclear Magnetic Shielding of Monoboranes: Calculation and Assessment of¹¹B NMR Chemical Shifts in Planar BX₃and in Tetrahedral [BX₄]⁻Systems

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Cationic closo‐carboranes 2. Do computed 11B and 13C NMR chemical shifts support their experimental availability?

Cited by 8 publications

References 42 publications

A computational analysis of the apparent nido vs. hypho conflict: are we dealing with six- or eight-vertex open-face diheteroboranes?

A computational analysis of the apparent nido vs. hypho conflict: are we dealing with six- or eight-vertex open-face diheteroboranes?

GIAO versus GIPAW: Comparison of Methods To Calculate 11B NMR Shifts of Icosahedral Closo-Heteroboranes toward Boron-Rich Borides

Nuclear Magnetic Shielding of Monoboranes: Calculation and Assessment of11B NMR Chemical Shifts in Planar BX3and in Tetrahedral [BX4]−Systems

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Cationic closo‐carboranes 2. Do computed ¹¹B and ¹³C NMR chemical shifts support their experimental availability?

GIAO versus GIPAW: Comparison of Methods To Calculate ¹¹B NMR Shifts of Icosahedral Closo-Heteroboranes toward Boron-Rich Borides

Nuclear Magnetic Shielding of Monoboranes: Calculation and Assessment of¹¹B NMR Chemical Shifts in Planar BX₃and in Tetrahedral [BX₄]⁻Systems