Skip to main content
Article
Lewis Base Mediated β-Elimination and Lewis Acid Mediated Insertion Reactions of Disilazido Zirconium Compounds
Journal of the American Chemical Society
  • KaKing Yan, Iowa State University
  • Juan J. Duchimaza Heredia, Iowa State University
  • Arkady Ellern, Iowa State University
  • Mark S. Gordon, Iowa State University
  • Aaron D. Sadow, Iowa State University
Document Type
Article
Disciplines
Publication Version
Published Version
Publication Date
9-25-2013
DOI
10.1021/ja407950e
Abstract
The reactivity of a series of disilazido zirconocene complexes is dominated by the migration of anionic groups (hydrogen, alkyl, halide, OTf) between the zirconium and silicon centers. The direction of these migrations is controlled by the addition of two-electron donors (Lewis bases) or two-electron acceptors (Lewis acids). The cationic nonclassical [Cp2ZrN(SiHMe2)2]+ ([2]+) is prepared from Cp2Zr{N(SiHMe2)2}H (1) and B(C6F5)3 or [Ph3C][B(C6F5)4], while reactions of B(C6F5)3 and Cp2Zr{N(SiHMe2)2}R (R = Me (3), Et (5), n-C3H7 (7), CH═CHSiMe3 (9)) provide a mixture of [2]+ and [Cp2ZrN(SiHMe2)(SiRMe2)]+. The latter products are formed through B(C6F5)3 abstraction of a β-H and R group migration from Zr to the β-Si center. Related β-hydrogen abstraction and X group migration reactions are observed for Cp2Zr{N(SiHMe2)2}X (X = OTf (11), Cl (13), OMe (15), O-i-C3H7 (16)). Alternatively, addition of DMAP (DMAP = 4-(dimethylamino)pyridine) to [2]+ results in coordination to a Si center and hydrogen migration to zirconium, giving the cationic complex [Cp2Zr{N(SiHMe2)(SiMe2DMAP)}H]+ ([19]+). Related hydrogen migration occurs from [Cp2ZrN(SiHMe2)(SiMe2OCHMe2)]+ ([18]+) to give [Cp2Zr{N(SiMe2DMAP)(SiMe2OCHMe2)}H]+ ([22]+), whereas X group migration is observed upon addition of DMAP to [Cp2ZrN(SiHMe2)(SiMe2X)]+ (X = OTf ([12]+), Cl ([14]+)) to give [Cp2Zr{N(SiHMe2)(SiMe2DMAP)}X]+ (X = OTf ([26]+), Cl ([20]+)). The species involved in these transformations are described by resonance structures that suggest β-elimination. Notably, such pathways are previously unknown in early metal amide chemistry. Finally, these migrations facilitate direct Si–H addition to carbonyls, which is proposed to occur through a pathway that previously had been reserved for later transition metal compounds.
Comments

Reprinted (adapted) with permission from Journal of the American Chemical Society 135 (2013): 15225, doi: 10.1021/ja407950e. Copyright 2013 American Chemical Society.

Copyright Owner
American Chemical Society
Language
en
File Format
application/pdf
Citation Information
KaKing Yan, Juan J. Duchimaza Heredia, Arkady Ellern, Mark S. Gordon, et al.. "Lewis Base Mediated β-Elimination and Lewis Acid Mediated Insertion Reactions of Disilazido Zirconium Compounds" Journal of the American Chemical Society Vol. 135 Iss. 40 (2013) p. 15225 - 15237
Available at: http://works.bepress.com/aaron_sadow/25/