De Chemische Binding

Dear members,

On the 15th of January, at 16.00h, the Career Committee organizes a lecture by Dr. Marc-Etienne Moret. The lecture will focus on the synthesis of stabilized silanides by nucleophilic substitution at silicon (II) and the abstract can be found below. Be sure to sign up for this very interesting lecture!

 

Free silanides, the anionic congeners of (base-stabilized) silylenes [1], are attractive synthetic targets as strong donor ligands for transition metals. The naked R3Si– fragment had previously been structurally characterized in zwitterionic silanides that encapsulate a metal in a remote ether [2] or pyrazole-based [3] binding site.
In this presentation, a novel synthesis of organic free silanide anions by complete substitution of an NHC-stabilized dichlorosilylene with trianionic, indolyl-based ligands is discussed
(Figure 1). The electron-withdrawing N-indolyl ligands stabilize the anionic Si(II) center sterically and electronically. The obtained silanides can be coordinated to various transition metals, including high-spin Fe(II) (Figure 1). In addition, the electronic stabilization of the anion is demonstrated by the exceptional acidity of the corresponding silane.
In addition, a computational investigation uncovers the relationship between a constrained cage geometry and the properties of the central silicon atom. In particular, valence angles constrained to ca. 90 degrees lower the energy a Si-centered lone pair with high s character, thereby stabilizing the pyramidal Si(II) state relative to tetrahedral Si(IV) derivatives.

References:

[1] Blom, B.; Stoelzel, M.; Driess, M. Chem. Eur. J. 19 (2013), 40.
[2] Carlson, B.; Aquino, A. J. A.; Hope-Weeks, L. J.; Whittlesey, B.; McNerney, B.; Hase, W. L.; Krempner, C. Chem.
Commun. 47 (2011), 11089.
[3] Armbruster, F.; Fernández, I.; Breher, F. Dalton Trans. 29 (2009) 5612.
[4] Witteman, L.; Evers, T.; Lutz, M.; Moret, M.-E. Chem. Eur. J. 51(2018) 3691.

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