DFT calculations of 29Si-NMR chemical shifts in Ru(ii) silyl complexes: Searching for trends and accurate values

Poblador‐Bahamonde, Amalia I.; Poteau, Romuald; Raynaud, Christophe; Eisenstein, Odile

doi:10.1039/c1dt11135c

Cited by 10 publications

(11 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Note that similar deviations were observed in the previous DFT studies of lighter metallosilyl compounds, with considerably smaller spin−orbit effects involved. 61,112 Several other levels (e.g., 2c-B3LYP and 4c-BP86) were tested during calibration, as well as different secondary references [(Me 3 Si) 3 SiH, (Me 3 Si) 4 Sn] for δ( 29 Si) (data not shown), but the 4c-PBE results could not be improved. Hence, 4c-PBE level is also used for discussing the 29 Si NMR.…”

Section: Resultsmentioning

confidence: 99%

High-Frequency ¹³C and ²⁹Si NMR Chemical Shifts in Diamagnetic Low-Valence Compounds of Tl^I and Pb^II: Decisive Role of Relativistic Effects

2016

View full text Add to dashboard Cite

The (13)C and (29)Si NMR signals of ligand atoms directly bonded to Tl(I) or Pb(II) heavy-element centers are predicted to resonate at very high frequencies, up to 400 ppm for (13)C and over 1000 ppm for (29)Si, outside the typical experimental NMR chemical-shift ranges for a given type of nuclei. The large (13)C and (29)Si NMR chemical shifts are ascribed to sizable relativistic spin-orbit effects, which can amount to more than 200 ppm for (13)C and more than 1000 ppm for (29)Si, values unexpected for diamagnetic compounds of the main group elements. The origin of the vast spin-orbit contributions to the (13)C and (29)Si NMR shifts is traced to the highly efficient 6p → 6p* metal-based orbital magnetic couplings and related to the 6p orbital-based bonding together with the low-energy gaps between the occupied and virtual orbital subspaces in the subvalent Tl(I) and Pb(II) compounds. New NMR spectral regions for these compounds are suggested based on the fully relativistic density functional theory calculations in the Dirac-Coulomb framework carefully calibrated on the experimentally known NMR data for Tl(I) and Pb(II) complexes.

show abstract

Section: Resultsmentioning

confidence: 99%

High-Frequency ¹³C and ²⁹Si NMR Chemical Shifts in Diamagnetic Low-Valence Compounds of Tl^I and Pb^II: Decisive Role of Relativistic Effects

2016

View full text Add to dashboard Cite

show abstract

“…The SO-HALA shielding contribution to the 29 Si NMR signals of − SiX 3 groups (X = H, C, and Cl) in 4d 6 Ru silyl complexes 158 was found to increase with the electronegativity of substituent X, with the maximum SO-HALA value of −35 ppm for X = Cl. 158 It has been suggested that this could be due to a smaller energy gap between the occupied and vacant MOs. However, an alternative explanation would be that the electronegative substituents increase the positive charge at Si and thus also the hybridization defects that increase the 3scharacter of Si in the Si−M bond, 46 thereby enhancing the SO/ FC mechanism of the SO-HALA effect (section 3.1.1).…”

Section: Trends In So-hala Shifts Across the Periodic Tablementioning

confidence: 91%

“…The SO-HALA shielding contribution to the 29 Si NMR signals of – SiX 3 groups (X = H, C, and Cl) in 4d 6 Ru silyl complexes was found to increase with the electronegativity of substituent X, with the maximum SO-HALA value of −35 ppm for X = Cl . It has been suggested that this could be due to a smaller energy gap between the occupied and vacant MOs.…”

Section: Trends In So-hala Shifts Across the Periodic Tablementioning

confidence: 99%

Relativistic Heavy-Neighbor-Atom Effects on NMR Shifts: Concepts and Trends Across the Periodic Table

et al. 2020

View full text Add to dashboard Cite

Chemical shifts present crucial information about an NMR spectrum. They show the influence of the chemical environment on the nuclei being probed. Relativistic effects caused by the presence of an atom of a heavy element in a compound can appreciably, even drastically, alter the NMR shifts of the nearby nuclei. A fundamental understanding of such relativistic effects on NMR shifts is important in many branches of chemical and physical science. This review provides a comprehensive overview of the tools, concepts, and periodic trends pertaining to the shielding effects by a neighboring heavy atom in diamagnetic systems, with particular emphasis on the "spin-orbit heavy-atom effect on the light-atom" NMR shift (SO-HALA effect). The analyses and tools described in this review provide guidelines to help NMR spectroscopists and computational chemists estimate the ranges of the NMR shifts for an unknown compound, identify intermediates in catalytic and other processes, analyze conformational aspects and intermolecular interactions, and predict trends in series of compounds throughout the Periodic Table . The present review provides a current snapshot of this important subfield of NMR spectroscopy and a basis and framework for including future findings in the field.

show abstract

“…Common organosilicon compounds such as alkyl silanes, silanols, and silyl ethers have already been studied with respect to the calculation of 29 Si NMR chemical shifts. − Nevertheless, more complex molecules containing, e.g., multiple bonded, transition metal bonded, and low-coordinate silicon are mainly studied in an experimental context or in very specialized studies − and lack a thorough comprehensive assessment. Compounds like triply bonded silicon compounds have been studied regarding the prediction of 29 Si NMR shifts.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive Benchmark Study on the Calculation of ²⁹Si NMR Chemical Shifts

et al. 2020

View full text Add to dashboard Cite

A comprehensive and diverse benchmark set for the calculation of 29 Si NMR chemical shifts is presented. The SiS146 set includes 100 silicon containing compounds with 146 experimentally determined reference 29 Si NMR chemical shifts measured in nine different solvents in a range from −400 to +828 ppm. Silicon atoms bound to main group elements as well as transition metals with coordination numbers of 2−6 in various bonding patterns including multiple bonds and coordinative and aromatic bonding are represented. The performance of various common and specialized density functional approximations including (meta-)GGA, hybrid, and double-hybrid functionals in combination with different AO basis sets and for differently optimized geometries is evaluated. The role of scalar-relativistic effects is further investigated by inclusion of the zeroth order regular approximation (ZORA) method into the calculations. GGA density functional approximations (DFAs) are found to outperform hybrid DFAs with B97-D3 performing best with an MAD of 7.2 ppm for the subset including only light atoms (Z < 18), while TPSSh is the best tested hybrid functional with an MAD of 10.3 ppm. For 29 Si cores in the vicinity of heavier atoms, the application of ZORA proved indispensable. Inclusion of spin−orbit effects into the 29 Si NMR chemical shift calculation decreases the mean absolute deviations by up to 74% compared to calculations applying effective core potentials.

show abstract

DFT calculations of 29Si-NMR chemical shifts in Ru(ii) silyl complexes: Searching for trends and accurate values

Cited by 10 publications

References 42 publications

High-Frequency ¹³C and ²⁹Si NMR Chemical Shifts in Diamagnetic Low-Valence Compounds of Tl^I and Pb^II: Decisive Role of Relativistic Effects

High-Frequency ¹³C and ²⁹Si NMR Chemical Shifts in Diamagnetic Low-Valence Compounds of Tl^I and Pb^II: Decisive Role of Relativistic Effects

Relativistic Heavy-Neighbor-Atom Effects on NMR Shifts: Concepts and Trends Across the Periodic Table

Comprehensive Benchmark Study on the Calculation of ²⁹Si NMR Chemical Shifts

Contact Info

Product

Resources

About

DFT calculations of 29Si-NMR chemical shifts in Ru(ii) silyl complexes: Searching for trends and accurate values

Cited by 10 publications

References 42 publications

High-Frequency 13C and 29Si NMR Chemical Shifts in Diamagnetic Low-Valence Compounds of TlI and PbII: Decisive Role of Relativistic Effects

High-Frequency 13C and 29Si NMR Chemical Shifts in Diamagnetic Low-Valence Compounds of TlI and PbII: Decisive Role of Relativistic Effects

Relativistic Heavy-Neighbor-Atom Effects on NMR Shifts: Concepts and Trends Across the Periodic Table

Comprehensive Benchmark Study on the Calculation of 29Si NMR Chemical Shifts

Contact Info

Product

Resources

About

High-Frequency ¹³C and ²⁹Si NMR Chemical Shifts in Diamagnetic Low-Valence Compounds of Tl^I and Pb^II: Decisive Role of Relativistic Effects

High-Frequency ¹³C and ²⁹Si NMR Chemical Shifts in Diamagnetic Low-Valence Compounds of Tl^I and Pb^II: Decisive Role of Relativistic Effects

Comprehensive Benchmark Study on the Calculation of ²⁹Si NMR Chemical Shifts