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TAS+(Z)-Me3CNSN- and TAS+(E)-Me3SiNSN-:  Does the Anion−Cation Interaction Influence the Configuration?

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posted on 17.08.2000, 00:00 by Tobias Borrmann, Andrey V. Zibarev, Enno Lork, Gerd Knitter, Shan-Jia Chen, Paul G. Watson, Edgardo Cutin, Makhmut M. Shakirov, Wolf-Dieter Stohrer, Rüdiger Mews
TAS+ salts (TAS = (Me2N)3S) of the sulfur diimide anions Me3XNSN- (X = C (1a), Si (1b)) were prepared by Si−N bond cleavage from the corresponding sulfur diimides Me3XNSNSiMe3 and TAS-fluoride ((Me2N)3S+Me3SiF2-) and characterized by X-ray crystallography and multinuclear NMR spectroscopy. According to the experimentally determined bond lengths and theoretical calculations, the Me3XNSN- anions are best described as thiazylamides Me3X−N−S⋮N rather than sulfur diimides Me3X−NSN. In agreement with the calculated and experimentally determined structures of the isoelectronic thionylimides RNSO, 1a adopts the Z-configuration, which is electronically favored due to anomeric effects. The electronically disfavored E-configuration of 1b in the solid state can be explained by weak anion−cation interaction.