Campus Units

Chemistry

Document Type

Article

Publication Version

Published Version

Publication Date

2016

Journal or Book Title

Organometallics

Volume

35

Issue

11

First Page

1674

Last Page

1683

DOI

10.1021/acs.organomet.6b00138

Abstract

The rare-earth bis(alkyl) compound Sm{C(SiHMe2)3}2THF2 (1b) is prepared by the reaction of samarium(II) iodide and 2 equiv of KC(SiHMe2)3. This synthesis is similar to that of previously reported Yb{C(SiHMe2)3}2THF2 (1a), and compounds 1a,b are isostructural. Reactions of 1b and 1 or 2 equiv of B(C6F5)3 afford SmC(SiHMe2)3HB(C6F5)3THF2 (2b) or Sm{HB(C6F5)3}2THF2 (3b), respectively, and 1,3-disilacyclobutane {Me2Si-C(SiHMe2)2}2 as a byproduct. Bands from 2300 to 2400 cm–1 assigned to νBH in the IR spectra and highly paramagnetically shifted signals in the 11B NMR spectra of 2b and 3b provided evidence for Sm-coordinated HB(C6F5)3. Compounds 1a,b react with the bulky N-heterocyclic carbene (NHC) 1,3-di-tert-butylimidazol-2-ylidene (ImtBu) to displace both THF ligands and give three-coordinate monoadducts Ln{C(SiHMe2)3}2ImtBu (Ln = Yb (4a), Sm (4b)). Complexes 4a,b catalyze cross-dehydrocoupling of organosilanes with primary and secondary amines at room temperature to give silazanes and H2, whereas 1a,b are not effective catalysts under these conditions. Second-order plots of ln{[Et2NH]/[Ph2SiH2]} vs time for 4a-catalyzed dehydrocoupling are linear and indicate first-order dependences on silane and amine concentrations. However, changes in the experimental rate law with increased silane concentration or decreased amine concentration reveal inhibition by silane. In addition, excess ImtBu or THF inhibit the reaction rate. These data, along with the structures of 4a,b, suggest that the bulky carbene favors low coordination numbers, which is important for accessing the catalytically active species.

Comments

This is an article from Organometallics 35 (2016): 1674, doi: 10.1021/acs.organomet.6b00138. Posted with permission.

Copyright Owner

American Chemical Society

Language

en

File Format

application/pdf

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