TAS(+)(Z)-Me3CNSN- and TAS(+)(E)-Me3SiNSN-: Does the anion-cation interaction influence the configuration?

TAS(+) salts (TAS = (Me2N)(3)S) 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)(3)S+Me3SiF2-) and ch aracterized by X-ray crystallography and multinuclear NMR spectroscopy. Acc ording to the experimentally determined bond lengths and theoretical calcul ations, 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 an d experimentally determined structures of the isoelectronic thionylimides R NSO, 1a adopts the 2-configuration, which is electronically favored due to anomeric effects. The electronically disfavored E-configuration of 1b in th e solid state can be explained by weak anion-cation interaction.