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Neufeld R, Michel R, Herbst-Irmer R, et al. Introducing a Hydrogen-Bond Donor into a Weakly Nucleophilic Brønsted Base: Alkali Metal Hexamethyldisilazides (MHMDS, M=Li, Na, K, Rb and Cs) with Ammonia. Chemistry. 2016;22(35):12340-6doi: 10.1002/chem.201600833.
Neufeld, R., Michel, R., Herbst-Irmer, R., Schöne, R., & Stalke, D. (2016). Introducing a Hydrogen-Bond Donor into a Weakly Nucleophilic Brønsted Base: Alkali Metal Hexamethyldisilazides (MHMDS, M=Li, Na, K, Rb and Cs) with Ammonia. Chemistry (Weinheim an der Bergstrasse, Germany), 22(35), 12340-6. https://doi.org/10.1002/chem.201600833
Neufeld, Roman, et al. "Introducing a Hydrogen-Bond Donor into a Weakly Nucleophilic Brønsted Base: Alkali Metal Hexamethyldisilazides (MHMDS, M=Li, Na, K, Rb and Cs) with Ammonia." Chemistry (Weinheim an der Bergstrasse, Germany) vol. 22,35 (2016): 12340-6. doi: https://doi.org/10.1002/chem.201600833
Neufeld R, Michel R, Herbst-Irmer R, Schöne R, Stalke D. Introducing a Hydrogen-Bond Donor into a Weakly Nucleophilic Brønsted Base: Alkali Metal Hexamethyldisilazides (MHMDS, M=Li, Na, K, Rb and Cs) with Ammonia. Chemistry. 2016 Aug 22;22(35):12340-6. doi: 10.1002/chem.201600833. Epub 2016 Jul 26. PMID: 27457218.
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Chemistry. 2016 Aug 22;22(35):12340-6. doi: 10.1002/chem.201600833. Epub 2016 Jul 26.

Introducing a Hydrogen-Bond Donor into a Weakly Nucleophilic Brønsted Base: Alkali Metal Hexamethyldisilazides (MHMDS, M=Li, Na, K, Rb and Cs) with Ammonia.

Chemistry (Weinheim an der Bergstrasse, Germany)

Roman Neufeld, Reent Michel, Regine Herbst-Irmer, Ralf Schöne, Dietmar Stalke

Affiliations

  1. Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, 37077, Göttingen, Germany.
  2. Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, 37077, Göttingen, Germany. [email protected].

PMID: 27457218 DOI: 10.1002/chem.201600833

Abstract

Alkali metal 1,1,1,3,3,3-hexamethyldisilazide (MHMDSs) are one of the most utilised weakly nucleophilic Brønsted bases in synthetic chemistry and especially in natural product synthesis. Like lithium organics, they aggregate depending on the employed donor solvents. Thus, they show different reactivity and selectivity as a function of their aggregation and solvation state. To date, monomeric LiHMDS with monodentate donor bases was only characterised in solution. Since the first preparation of LiHMDS in 1959 by Wannagat and Niederprüm, all efforts to crystallise monomeric LiHMDS in the absence of chelating ligands failed. Herein, we present ammonia adducts of LiHMDS, NaHMDS, KHMDS, RbHMDS and CsHMDS with unprecedented aggregation motifs: 1) The hitherto missing monomeric key compound in the LiHMDS aggregation architectures. Monomeric crystal structures of trisolvated LiHMDS (1) and NaHMDS (2), showing unique intermolecular hydrogen bonds, 2) the unprecedented tetrasolvated KHMDS (3) and RbHMDS (4) dimers and 3) the disolvated CsHMDS (5) dimer with very close intermolecular Si-CH3 ⋅⋅⋅Cs s-block "agostic" interactions have been prepared and characterised by single-crystal X-ray structure analysis.

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Keywords: X-ray diffraction; amides; hydrogen bonds; reactive intermediates; solvent effects

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