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Title: The Nature of Secondary Interactions at Electrophilic Metal Sites of Molecular and Silica-Supported Organolutetium Complexes from Solid-State NMR Spectroscopy

Abstract

Lu[CH(SiMe3)2]3 reacts with [SiO2-700] to give [(≡SiO)Lu[CH(SiMe3)2]2] and CH2(SiMe3)2. [(≡SiO)Lu[CH(SiMe3)2]2] is characterized by solid-state NMR and EXAFS spectroscopy, which show that secondary Lu···C and Lu···O interactions, involving a γ-CH3 and a siloxane bridge, are present. From X-ray crystallographic analysis, the molecular analogues Lu[CH(SiMe3)2]3-x[O-2,6-tBu-C6H3]x (x = 0-2) also have secondary Lu···C interactions. The 1H NMR spectrum of Lu[CH(SiMe3)2]3 shows that the -SiMe3 groups are equivalent to -125°C and inequivalent below that temperature, δ‡(Tc= 148 K)= 7.1 kcal mol-1. Both -SiMe3 groups in Lu[CH(SiMe3)2]3 have 1JCH = 117 ± 1 Hz at -140°C. The solid-state 13C CPMAS NMR spectrum at 20°C shows three chemically inequivalent resonances in the area ratio of 4:1:1 (12:3:3); the J-resolved spectra for each resonance give 1JCH = 117 ± 2 Hz. The 29Si CPMAS NMR spectrum shows two chemically inequivalent resonances with different values of chemical shift anisotropy. Similar observations are obtained for Lu[CH(SiMe3)2]3-x[O-2,6-tBu-C6H3]x (x = 1 and 2). The spectroscopic data point to short Lu···Cγ contacts corresponding to 3c-2e Lu···Cγ-Siβ interactions, which are supported by DFT calculations. Calculated natural bond orbital (NBO) charges show that Cγ carries a negative charge, while Lu, Hγ, and Siβ carry positive charges; as the number of O-based ligands increases somore » does the positive charge at Lu, which in turns shortens the Lu···Cγ distance. Finally, the change in NBO charges and the resulting changes in the spectroscopic and crystallographic properties show how ligands and surface-support sites rearrange to accommodate these changes, consistent with Pauling's electroneutrality concept.« less

Authors:
 [1];  [1];  [2];  [2];  [2];  [3];  [3];  [4];  [1];  [5]
  1. Federal Inst. of Technology, Zurich (Switzerland). Dept. of Chemistry and Applied Biosciences
  2. Univ. de Lyon, Villeurbanne (France). Centre de RMN à Très Hauts Champs
  3. Univ. de Toulouse (France)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division
  5. Univ. of California, Berkeley, CA (United States). Dept. of Chemistry
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1482511
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 138; Journal Issue: 11; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Conley, Matthew P., Lapadula, Giuseppe, Sanders, Kevin, Gajan, David, Lesage, Anne, del Rosal, Iker, Maron, Laurent, Lukens, Wayne W., Copéret, Christophe, and Andersen, Richard A. The Nature of Secondary Interactions at Electrophilic Metal Sites of Molecular and Silica-Supported Organolutetium Complexes from Solid-State NMR Spectroscopy. United States: N. p., 2016. Web. doi:10.1021/jacs.6b00071.
Conley, Matthew P., Lapadula, Giuseppe, Sanders, Kevin, Gajan, David, Lesage, Anne, del Rosal, Iker, Maron, Laurent, Lukens, Wayne W., Copéret, Christophe, & Andersen, Richard A. The Nature of Secondary Interactions at Electrophilic Metal Sites of Molecular and Silica-Supported Organolutetium Complexes from Solid-State NMR Spectroscopy. United States. doi:10.1021/jacs.6b00071.
Conley, Matthew P., Lapadula, Giuseppe, Sanders, Kevin, Gajan, David, Lesage, Anne, del Rosal, Iker, Maron, Laurent, Lukens, Wayne W., Copéret, Christophe, and Andersen, Richard A. Tue . "The Nature of Secondary Interactions at Electrophilic Metal Sites of Molecular and Silica-Supported Organolutetium Complexes from Solid-State NMR Spectroscopy". United States. doi:10.1021/jacs.6b00071. https://www.osti.gov/servlets/purl/1482511.
@article{osti_1482511,
title = {The Nature of Secondary Interactions at Electrophilic Metal Sites of Molecular and Silica-Supported Organolutetium Complexes from Solid-State NMR Spectroscopy},
author = {Conley, Matthew P. and Lapadula, Giuseppe and Sanders, Kevin and Gajan, David and Lesage, Anne and del Rosal, Iker and Maron, Laurent and Lukens, Wayne W. and Copéret, Christophe and Andersen, Richard A.},
abstractNote = {Lu[CH(SiMe3)2]3 reacts with [SiO2-700] to give [(≡SiO)Lu[CH(SiMe3)2]2] and CH2(SiMe3)2. [(≡SiO)Lu[CH(SiMe3)2]2] is characterized by solid-state NMR and EXAFS spectroscopy, which show that secondary Lu···C and Lu···O interactions, involving a γ-CH3 and a siloxane bridge, are present. From X-ray crystallographic analysis, the molecular analogues Lu[CH(SiMe3)2]3-x[O-2,6-tBu-C6H3]x (x = 0-2) also have secondary Lu···C interactions. The 1H NMR spectrum of Lu[CH(SiMe3)2]3 shows that the -SiMe3 groups are equivalent to -125°C and inequivalent below that temperature, δ‡(Tc= 148 K)= 7.1 kcal mol-1. Both -SiMe3 groups in Lu[CH(SiMe3)2]3 have 1JCH = 117 ± 1 Hz at -140°C. The solid-state 13C CPMAS NMR spectrum at 20°C shows three chemically inequivalent resonances in the area ratio of 4:1:1 (12:3:3); the J-resolved spectra for each resonance give 1JCH = 117 ± 2 Hz. The 29Si CPMAS NMR spectrum shows two chemically inequivalent resonances with different values of chemical shift anisotropy. Similar observations are obtained for Lu[CH(SiMe3)2]3-x[O-2,6-tBu-C6H3]x (x = 1 and 2). The spectroscopic data point to short Lu···Cγ contacts corresponding to 3c-2e Lu···Cγ-Siβ interactions, which are supported by DFT calculations. Calculated natural bond orbital (NBO) charges show that Cγ carries a negative charge, while Lu, Hγ, and Siβ carry positive charges; as the number of O-based ligands increases so does the positive charge at Lu, which in turns shortens the Lu···Cγ distance. Finally, the change in NBO charges and the resulting changes in the spectroscopic and crystallographic properties show how ligands and surface-support sites rearrange to accommodate these changes, consistent with Pauling's electroneutrality concept.},
doi = {10.1021/jacs.6b00071},
journal = {Journal of the American Chemical Society},
number = 11,
volume = 138,
place = {United States},
year = {2016},
month = {3}
}

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