Residual 31P, 35,37Cl dipolar coupling in 31P MAS spectra of chlorocyclophosphazenes

In ³¹P MAS NMR spectra of chlorocyclophosphazenes, characteristic splittings have been observed for PCl or PCl₂ groups. At different applied magnetic fields, the fine structure and total width of the patterns change in a characteristic way, demonstrating that the splittings are due to indirect spin–spin and residual dipolar interactions with the chlorine nuclei directly bonded to phosphorus. For trans-nongeminal N₃P₃Cl₃(NMe₂)₃ and N₃P₃Cl₆ as examples, the spectra have been analyzed to obtain information on chlorine nuclear quadrupole coupling constants and ^35,37Cl, ³¹P indirect spin–spin coupling constants. Neglect of these interactions may result in misinterpretations of the multiplicity in ³¹P MAS spectra of chlorophosphazenes.