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Homoleptic Trivalent Tris(alkyl) Rare Earth Compounds
Journal of the American Chemical Society
  • Aradhana Pindwal, Iowa State University and Ames Laboratory
  • KaKing Yan, Iowa State University and Ames Laboratory
  • Smita Patnaik, Iowa State University and Ames Laboratory
  • Bradley M. Schmidt, Iowa State University and Ames Laboratory
  • Arkady Ellern, Iowa State University
  • Igor I. Slowing, Iowa State University and Ames Laboratory
  • Cheolbeom Bae, Kumho Petrochemical R&D Center
  • Aaron D. Sadow, Iowa State University and Ames Laboratory
Document Type
Article
Publication Version
Accepted Manuscript
Publication Date
10-9-2017
DOI
10.1021/jacs.7b09521
Abstract

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 LnI(3)THF(n) and 3 equiv of KC(SiHMe2)(3). X-ray diffraction studies reveal 1a-d are isostructural, pseudo-C-3-symmetric molecules that contain two secondary Li <- HSi interactions per alkyl ligand (six total). Spectroscopic assignments are supported by comparison with Ln{C(SiDMe2)(3)}(3) and DFT calculations. 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 la (Delta H-double dagger = 8.2(4) kcal.mol(-1); Delta S-double dagger = -1(2) cal.mol(-1)K(-1)) and 1a-d(9) (Delta H-double dagger = 7.7(3) kcal.mol(-1); Delta S-double dagger = -4(2) cal.mol(-1)K(-1)). Comparisons of lineshapes, rate constants, (k(H)/k(D)), and slopes of ln (k/T) vs 1/T plots for la and 1a-d(9) reveal that an inverse isotope effect dominates at low temperature. DFT calculations identify four low-energy intermediates containing five beta-Si-H -> Ln and one gamma-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 degrees 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(Ox(Me2))(2)) give {MeC(Ox(Me2))(2)}Ln{C(SiHMe2)(3)}(2), and reactions with disilazanes provide solvent-free lanthanoid tris(disilazides).

Comments

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see 10.1021/jacs.7b09521. Posted with permission.

Copyright Owner
American Chemical Society
Language
en
File Format
application/pdf
Citation Information
Aradhana Pindwal, KaKing Yan, Smita Patnaik, Bradley M. Schmidt, et al.. "Homoleptic Trivalent Tris(alkyl) Rare Earth Compounds" Journal of the American Chemical Society Vol. 139 Iss. 46 (2017) p. 16862 - 16874
Available at: http://works.bepress.com/igor_slowing/65/