Inverse halogen dependence in anion <sup>13</sup>C NMR

Viesser, Renan V.; Tormena, Cláudio F.

doi:10.1039/d0cp05891b

Cited by 3 publications

(3 citation statements)

References 64 publications

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“…These results demonstrate that the simple charge−shift correlation is unlikely to be sufficient for a detailed understanding of NMR shielding [77,112] . While partial charges might be a qualitatively good measure for the overall deshielding, they are hardly sensitive indicators for the factors that determine the 103 Rh NMR shifts.…”

Section: Resultsmentioning

confidence: 92%

“…These results demonstrate that the simple chargeÀ shift correlation is unlikely to be sufficient for a detailed understanding of NMR shielding. [77,112] While partial charges might be a qualitatively good measure for the overall deshielding, they are hardly sensitive indicators for the factors that determine the 103 Rh [108] For heteroleptic compounds 8 and 11-18, the chemical shifts of 103 Rh connected to À NH are marked in blue. For hypothetical compounds trans-9 • 2MeCN and cis-10' (no axial MeCN), here denoted as 9 and 10' (see the text for details), the chemical shifts of 103 Rh are marked in gray.…”

Section: Rh Nmr Chemical Shiftmentioning

confidence: 99%

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Elucidating the Electronic Nature of Rh‐based Paddlewheel Catalysts from ¹⁰³Rh NMR Chemical Shifts: Insights from Quantum Mechanical Calculations

Gui,

Sorbelli,

Caló

et al. 2023

Chemistry A European J

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The tremendous importance of dirhodium paddlewheel com‐plexes for asymmetric catalysis is largely the result of anempirical optimization of the chiral ligand sphere aboutthe bimetallic core. Only recently, a H(C)Rhtriple resonance 103Rh NMR experiment provided the long‐awaited opportunity to examine – with previously incon‐ceivable accuracy – how variation of the ligands impacts onthe electronic structure of such catalysts. The recorded ef‐fects are dramatic: formal replacement of one out ofeight O‐atoms in a dirhodium tetracarboxylate by an N‐atom results in a shielding of thecorresponding Rh‐site of no less than 1000 ppm. The cur‐rent paper provides the framework that allowsthis and related experimental observations made with a setof 19 representative rhodium complexes to be interpreted.In line with symmetry considerations, it is shown that theshielding tensor responds only to the donor ability of theequatorial ligands along the perpendicular principal axis.Axial ligands, in contrast, have no direct effect on shield‐ing but exert an electronic cis‐effect that onto the neighboring equatorial sites. Furthermore, charge redistribution within the core as well as the electronic trans‐effect of ligands ofdifferent donor strengths is reflected in the 103 Rh NMR shifts.

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Section: Resultsmentioning

confidence: 92%

Section: Rh Nmr Chemical Shiftmentioning

confidence: 99%

Elucidating the Electronic Nature of Rh‐based Paddlewheel Catalysts from ¹⁰³Rh NMR Chemical Shifts: Insights from Quantum Mechanical Calculations

Gui,

Sorbelli,

Caló

et al. 2023

Chemistry A European J

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“…The principal components of the CST (δ 11 , δ 22 , δ 33 with δ 11 ≥ δ 22 ≥ δ 33 ) have been shown to be controlled mainly by the paramagnetic terms, which themselves can be understood on the basis of the couplings between occupied and vacant molecular orbitals (MOs) having contributions on the NMR active atom and its immediate environment. This analysis has provided valuable insight into the electronic structure of various molecules and their reactivity, − but studies of halogen-bonded systems are rare. A pioneer example is the analysis of the 13 C NMR shielding tensor of the C–I bond in diiodoacetylene acting as XB donor with amines, where the observed and calculated deshielding at the iodine-bonded carbon was traced back to a contribution from the paramagnetic coupling of the occupied π MOs of the alkyne with the vacant σ C–I * MO.…”

Section: Introductionmentioning

confidence: 99%

Solid-State ¹⁹F NMR Chemical Shift in Square-Planar Nickel–Fluoride Complexes Linked by Halogen Bonds

et al. 2023

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The halogen bond (XB) is a highly directional class of noncovalent interactions widely explored by experimental and computational studies. However, the NMR signature of the XB has attracted limited attention. The prediction and analysis of the solidstate NMR (SSNMR) chemical shift tensor provide useful strategies to better understand XB interactions. In this work, we employ a computational protocol for modeling and analyzing the 19 F SSNMR chemical shifts previously measured in a family of square-planar trans Ni II -L 2 -iodoaryl-fluoride (L = PEt 3 ) complexes capable of forming self-complementary networks held by a NiF••• I(C) halogen bond [Thangavadivale, V.; et al. Chem. Sci. 2018, 9, 3767−3781]. To understand how the 19 F NMR resonances of the nickel-bonded fluoride are affected by the XB, we investigate the origin of the shielding in trans-[NiF(2,3,5,6-C 6 F 4 I)(PEt 3 ) 2 ], trans-[NiF(2,3,4,5-C 6 F 4 I)(PEt 3 ) 2 ], and trans-[NiF(C 6 F 5 )(PEt 3) 2 ] in the solid state, where a XB is present in the two former systems but not in the last. We perform the 19 F NMR chemical shift calculations both in periodic and molecular models. The results show that the crystal packing has little influence on the NMR signatures of the XB, and the NMR can be modeled successfully with a pair of molecules interacting via the XB. Thus, the observed difference in chemical shift between solid-state and solution NMR can be essentially attributed to the XB interaction. The very high shielding of the fluoride and its driving contributor, the most shielded component of the chemical shift tensor, are well reproduced at the 2c-ZORA level. Analysis of the factors controlling the shielding shows how the highest occupied Ni/F orbitals shield the fluoride in the directions perpendicular to the Ni−F bond and specifically perpendicular to the coordination plane. This shielding arises from the magnetic coupling of the Ni(3d)/F(2p lone pair) orbitals with the vacant σ Ni−F * orbital, thereby rationalizing the very highly upfield (shielded) resonance of the component (δ 33 ) along this direction. We show that these features are characteristic of square-planar nickel−fluoride complexes. The deshielding of the fluoride in the halogen-bonded systems is attributed to an increase in the energy gap between the occupied and vacant orbitals that are mostly responsible for the paramagnetic terms, notably along the most shielded direction.

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Influence of stereoelectronic interactions on the 13C NMR chemical shift in iodine-containing molecules

Viesser¹,

Tormena²

2022

Journal of Magnetic Resonance Open

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Inverse halogen dependence in anion ¹³C NMR

Abstract: A guideline to interpret the magnitude and sign of diamagnetic, paramagnetic, and spin–orbit coupling mechanisms of the 13C shielding tensor in neutral, cationic, and anionic molecules.

Cited by 3 publications

References 64 publications

Elucidating the Electronic Nature of Rh‐based Paddlewheel Catalysts from ¹⁰³Rh NMR Chemical Shifts: Insights from Quantum Mechanical Calculations

Elucidating the Electronic Nature of Rh‐based Paddlewheel Catalysts from ¹⁰³Rh NMR Chemical Shifts: Insights from Quantum Mechanical Calculations

Solid-State ¹⁹F NMR Chemical Shift in Square-Planar Nickel–Fluoride Complexes Linked by Halogen Bonds

Influence of stereoelectronic interactions on the 13C NMR chemical shift in iodine-containing molecules

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Inverse halogen dependence in anion 13C NMR

Abstract: A guideline to interpret the magnitude and sign of diamagnetic, paramagnetic, and spin–orbit coupling mechanisms of the 13C shielding tensor in neutral, cationic, and anionic molecules.

Cited by 3 publications

References 64 publications

Elucidating the Electronic Nature of Rh‐based Paddlewheel Catalysts from 103Rh NMR Chemical Shifts: Insights from Quantum Mechanical Calculations

Elucidating the Electronic Nature of Rh‐based Paddlewheel Catalysts from 103Rh NMR Chemical Shifts: Insights from Quantum Mechanical Calculations

Solid-State 19F NMR Chemical Shift in Square-Planar Nickel–Fluoride Complexes Linked by Halogen Bonds

Influence of stereoelectronic interactions on the 13C NMR chemical shift in iodine-containing molecules

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Inverse halogen dependence in anion ¹³C NMR

Elucidating the Electronic Nature of Rh‐based Paddlewheel Catalysts from ¹⁰³Rh NMR Chemical Shifts: Insights from Quantum Mechanical Calculations

Elucidating the Electronic Nature of Rh‐based Paddlewheel Catalysts from ¹⁰³Rh NMR Chemical Shifts: Insights from Quantum Mechanical Calculations

Solid-State ¹⁹F NMR Chemical Shift in Square-Planar Nickel–Fluoride Complexes Linked by Halogen Bonds