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 PCI 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, 3P indirect spin-spin coupling constants. Neglect of these interactions may result in misinterpretations of the multiplicity in 3P MAS spectra of chlorophosphazenes.