Chlorine-35 nuclear quadrupole resonance studies of some six-membered ring systems containing nitrogen, sulphur, and/or phosphorus : α-(NSClO)3, cis-(NSClO)2(NPCl2), and (NSClO)(NPCl2)2

Abstract

Chlorine-35 n.q.r. spectra for α-(NSClO)₃, cis-(NSClO)₂(NPCl₂), and (NSClO)(NPCl₂)₂ have been recorded in the temperature range 77–300 K. Spectra have also been examined for these substances at 293 K when subjected to pressures within the range 1–700 kg cm^–2 : the chlorine-35 resonance frequencies are linear functions of pressure. The partial differential coefficients (∂ν/∂P)_T at 293 K, (∂ν/∂T)_P, at 1 kg cm^–2 and 293 K, and (∂ν/∂T)_v, at 293 K have been evaluated for each resonance frequency and are related to the molecular conformers present in these solids. At 165 K (NSClO)(NPCl₂)₂ undergoes a phase change in which the conformation of the six-membered ring changes. The chlorine resonance frequencies, ν/MHz, are related to the corresponding bond lengths, d/Å: these relationships are d=–0.0152ν+ 2.4166 for P–Cl bonds and d=–0.0172ν+ 2.636 for S–Cl bonds. The NSClO group is more electronegative than the NPCl₂ group. Chlorine valence-electron populations, ϕ, can be deduced from the corresponding chlorine-35 n.q.r. frequencies at 77 K. The appropriate relationships are ϕ=–0.034₅ν+ 8 for P–Cl bonds and ϕ=–0.026₅ν+ 8 for SClO groups.