Sulphur–nitrogen anions: ¹⁴N and ¹⁵N NMR investigations of the deprotonation of cyclic sulphur imides and sulphur–ammonia solutions

Abstract

The following systems have been investigated by 1 4~ and ( o r ) 1 5~ NMR spectroscopy: (a) the deprotonation of S7NH by n-BuLi, (b) solutions of S,, S7NH, 1,3-and 1 ,4-S6(NH),, and K2SNZ in liquid ammonia, (c) the reaction of sodium azide with sulphur in hexamethylphosphoramide (HMPA), (4 the reactions of S7NH and S4(NH), with potassium amide in liquid ammonia in various molar ratios, and (e) the reaction of (NSCI), with potassium amide (1 :6 molar ratio) in liquid ammonia. These investigations have provided an NMR characterization of the thermally unstable S7N-( 6 "~ ca.-324 ppm) and S2N2H-ions ( 6 1 4~ + 7 and -149 ppm, 'J('~N-'H) 36 Hz, 'J("N-H) 55 Hz, -J("N-'~N) 2.2 Hz) in liquid ammonia, demonstrated the existence of S7N-, in addition to SSNSS-, as the major nitrogen-containing ingredient of sulphur-ammonia solutions (SAS), and confirmed the formation of the SSNSS-, but not S7N-, from the reaction of sodium azide and sulphur in HMPA. Consistent with previous chemical investigations, the NMR data show that the S7N-and S,N,H-ions are thermally unstable with respect to the formation of SSNSS-and S,N,-, respectively, in solution. Solutions of S4(NH),/4KNHI or (NSC1),/6KNH2 show the same two "N or "N NMR resonances at ca. +97 and -108 ppm as a solution of NSN'-in liquid ammonia.

A Variable Temperature X-ray Diffraction Investigation of [PPN+][S4N5−]: Supramolecular Interactions Governing an Order/Disorder Transformation and the First High Resolution X-ray Structure of the Anion

“…In a short period in time, this cation was used to isolate thermally stable salts of S 4 N − , S 3 N 3 − and S 4 N 5 − (Figure 1) [5,6,7]. These stable, safe and thus transportable salts have enabled thorough investigations of properties such as 14 N- and 15 N- NMR spectroscopy [10,18,19,20], voltammetry and EPR spectroelectrochemistry [21,22,23,24], vibrational circular dichroism spectroscopy [25,26] and reactivity [8,27,28] including the generation of free radicals [29,30].…”

Theoretical analysis of solvent effects on nitrogen NMR chemical shifts in oxazoles and oxadiazoles

“…Especially, the nitrogen magnetic shielding turned out to be very sensitive to a solvent [2]. The solvent effect on the nitrogen nuclear magnetic shielding has been investigated both experimentally [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and theoretically [20][21][22][23][24][25][26][27][28][29][30][31][32]. In particular, the solvent effects on the 14 N magnetic shielding in 5-and 6-membered hetero-aromatic compounds have been extensively studied experimentally by Witanowski et al [3][4][5][6][7][8][9].…”