Lewis Base Mediated beta-Elimination and Lewis Acid Mediated Insertion Reactions of Disilazido Zirconium Compounds

Thumbnail Image
Supplemental Files
Date
2013-09-01
Authors
Yan, KaKing
Heredia, Juan
Ellern, Arkady
Gordon, Mark
Sadow, Aaron
Major Professor
Advisor
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Authors
Research Projects
Organizational Units
Organizational Unit
Journal Issue
Is Version Of
Versions
Series
Department
Chemistry
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 beta-H and R group migration from Zr to the beta-Si center. Related beta-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)(SiMe(2)DMAP)}H+ ([19](+)). Related hydrogen migration occurs from [Cp2ZrN(SiHMe2)(SiMe2OCHMe2)](+) ([18](+)) to give [Cp2Zr{N(SiMe(2)DMAP)(SiMe2OCHMe2)}H](+) ([22](+)), whereas X group migration is observed upon addition of DMAP to [Cp2ZrN(SiHMe2)(SiMe2X)](+) (X = OTf ([12](+)), CI ([14](+))) to give [Cp2Zr{N(SiHMe2)(SiMe(2)DMAP)}X](+) (X = OTf ([26]+), Cl ([20]+)). The species involved in these transformations are described by resonance structures that suggest beta-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.

Description
Keywords
Citation
DOI
Subject Categories
Copyright
Tue Jan 01 00:00:00 UTC 2013
Collections