skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Homoleptic Trivalent Tris(alkyl) Rare Earth Compounds

Abstract

Homoleptic tris(alkyl) rare earth complexes Ln{C(SiHMe 2) 3} 3 (Ln = La, 1a; Ce, 1b; Pr, 1c; Nd, 1d) are synthesized in high yield from LnI 3THF n and 3 equiv of KC(SiHMe 2) 3. X-ray diffraction studies reveal 1a–d are isostructural, pseudo-C 3-symmetric molecules that contain two secondary Ln←HSi interactions per alkyl ligand (six total). Spectroscopic assignments are supported by comparison with Ln{C(SiDMe 2) 3} 3 and DFT calculations. Here, the Ln←HSi and terminal SiH exchange rapidly on the NMR time scale at room temperature, but the two motifs are resolved at low temperature. Variable-temperature NMR studies provide activation parameters for the exchange process in 1a (ΔH = 8.2(4) kcal·mol –1; ΔS = –1(2) cal·mol –1K –1) and 1a-d 9 (ΔH = 7.7(3) kcal·mol –1; ΔS = –4(2) cal·mol –1K –1). Comparisons of lineshapes, rate constants (kH/kD), and slopes of ln(k/T) vs 1/T plots for 1a and 1a-d 9 reveal that an inverse isotope effect dominates at low temperature. DFT calculations identify four low-energy intermediates containing five β-Si–H→Ln and one γ-C–H→Ln. The calculations also suggest the pathway for Ln←HSi/SiH exchange involves rotation of a single C(SiHMe 2) 3 ligand that is coordinated to the Lnmore » center through the Ln–C bond and one secondary interaction. These robust organometallic compounds persist in solution and in the solid state up to 80 °C, providing potential for their use in a range of synthetic applications. For example, reactions of Ln{C(SiHMe 2) 3} 3 and ancillary proligands, such as bis-1,1-(4,4-dimethyl-2-oxazolinyl)ethane (HMeC(Ox Me2) 2) give {MeC(Ox Me2) 2}Ln{C(SiHMe 2) 3} 2, and reactions with disilazanes provide solvent-free lanthanoid tris(disilazides).« less

Authors:
ORCiD logo [1];  [1];  [1];  [1];  [2]; ORCiD logo [1];  [3]; ORCiD logo [1]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States)
  2. Iowa State Univ., Ames, IA (United States)
  3. Kumbo Petrochemical R&D Center, Daejeon (Republic of Korea)
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1411958
Report Number(s):
IS-J-9441
Journal ID: ISSN 0002-7863; TRN: US1800290
Grant/Contract Number:
AC02-07CH11358
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 139; Journal Issue: 46; 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

Pindwal, Aradhana, Yan, KaKing, Patnaik, Smita, Schmidt, Bradley M., Ellern, Arkady, Slowing, Igor I., Bae, Cheolbeom, and Sadow, Aaron D. Homoleptic Trivalent Tris(alkyl) Rare Earth Compounds. United States: N. p., 2017. Web. doi:10.1021/jacs.7b09521.
Pindwal, Aradhana, Yan, KaKing, Patnaik, Smita, Schmidt, Bradley M., Ellern, Arkady, Slowing, Igor I., Bae, Cheolbeom, & Sadow, Aaron D. Homoleptic Trivalent Tris(alkyl) Rare Earth Compounds. United States. doi:10.1021/jacs.7b09521.
Pindwal, Aradhana, Yan, KaKing, Patnaik, Smita, Schmidt, Bradley M., Ellern, Arkady, Slowing, Igor I., Bae, Cheolbeom, and Sadow, Aaron D. Mon . "Homoleptic Trivalent Tris(alkyl) Rare Earth Compounds". United States. doi:10.1021/jacs.7b09521.
@article{osti_1411958,
title = {Homoleptic Trivalent Tris(alkyl) Rare Earth Compounds},
author = {Pindwal, Aradhana and Yan, KaKing and Patnaik, Smita and Schmidt, Bradley M. and Ellern, Arkady and Slowing, Igor I. and Bae, Cheolbeom and Sadow, Aaron D.},
abstractNote = {Homoleptic tris(alkyl) rare earth complexes Ln{C(SiHMe2)3}3 (Ln = La, 1a; Ce, 1b; Pr, 1c; Nd, 1d) are synthesized in high yield from LnI3THFn and 3 equiv of KC(SiHMe2)3. X-ray diffraction studies reveal 1a–d are isostructural, pseudo-C3-symmetric molecules that contain two secondary Ln←HSi interactions per alkyl ligand (six total). Spectroscopic assignments are supported by comparison with Ln{C(SiDMe2)3}3 and DFT calculations. Here, the Ln←HSi and terminal SiH exchange rapidly on the NMR time scale at room temperature, but the two motifs are resolved at low temperature. Variable-temperature NMR studies provide activation parameters for the exchange process in 1a (ΔH‡ = 8.2(4) kcal·mol–1; ΔS‡ = –1(2) cal·mol–1K–1) and 1a-d9 (ΔH‡ = 7.7(3) kcal·mol–1; ΔS‡ = –4(2) cal·mol–1K–1). Comparisons of lineshapes, rate constants (kH/kD), and slopes of ln(k/T) vs 1/T plots for 1a and 1a-d9 reveal that an inverse isotope effect dominates at low temperature. DFT calculations identify four low-energy intermediates containing five β-Si–H→Ln and one γ-C–H→Ln. The calculations also suggest the pathway for Ln←HSi/SiH exchange involves rotation of a single C(SiHMe2)3 ligand that is coordinated to the Ln center through the Ln–C bond and one secondary interaction. These robust organometallic compounds persist in solution and in the solid state up to 80 °C, providing potential for their use in a range of synthetic applications. For example, reactions of Ln{C(SiHMe2)3}3 and ancillary proligands, such as bis-1,1-(4,4-dimethyl-2-oxazolinyl)ethane (HMeC(OxMe2)2) give {MeC(OxMe2)2}Ln{C(SiHMe2)3}2, and reactions with disilazanes provide solvent-free lanthanoid tris(disilazides).},
doi = {10.1021/jacs.7b09521},
journal = {Journal of the American Chemical Society},
number = 46,
volume = 139,
place = {United States},
year = {Mon Oct 09 00:00:00 EDT 2017},
month = {Mon Oct 09 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on October 9, 2018
Publisher's Version of Record

Save / Share: