Various six-membered cyclic sulfur diimides (3a—f) were prepared by aminolysis of the bis(chloro-dimethylsilyl)sulfur diimide (2) using NH3 (a) and primary amines RNH2 [R = Me (b), Et (c), nPr (d), nBu (e), iPr (f)]. Except for R = H, non-cyclic intermediates, the Si-monoamino- (7) and Si,Si′-diamino derivatives of 2 (8), were detetected for all groups R, including R = tBu (g). The reaction between R2SiCl2 and the sulfur diimide anion K[(NSN)SiMe3] gave non-cyclic silanes (9,10) and the eight-membered rings of the type R2Si(NSN)2SiR2 [R = Me (4), tBu (5)] of which 5 was studied by X-ray analysis (monoclinic, space group P21/c; planar ring system) and solid-state 15N and 29Si CP/MAS NMR spectroscopy. The ten-membered ring system 6 was obtained from the reaction between 1,2-dichlorotetramethyldisilane and bis(trimethylstannyl)sulfur diimide. All compounds were studied by 1H,13C, 15N and 29Si NMR. The δ15N NMR data proved useful to distinguish between fluxional systems with fast E/Z—Z/E isomerization (non-cyclic compounds 8 and the ten-membered cycle 6). Hahn-Echo-extended (HEED) polarization transfer (INEPT) pulse sequences served to measure coupling constants 1J(29Si15Namine) for the compounds 3 and 8. This also proved that the magnitude of 1J(29Si15NNSN) must be small (< 1 Hz). In the case of the compounds 3, the rather small magnitude of both 1J(29Si15Namine) and 1J(15N1H) (3a) indicated that the aminonitrogen atom adopts a pyramidal environment.
Use of 15N NMR spectroscopy to probe covalency in a thorium nitride