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Chlorine-35 nuclear quadrupole resonance frequencies, ν, in N 3 P 3 Cl 6 and in N 3 P 3 Cl 5 NH Pr i are linear functions of the applied pressure, P , within the range 1 to 1000 kg·cm −2 . Chlorine-35 nuclear quadrupole resonance frequencies in N 3 P 3 Cl 5 NH Pr i , examined over the temperature range 100 to 320 K, have revealed that this solid undergoes a sharp phase change over the temperature range 220 to 235 K. Values of the partial differential coefficients. have been evaluated for each of the resonance frequencies in N 3 P 3 Cl 6 and in N 3 P 3 Cl 5 NH Pr i . The applied pressure discriminates between the two kinds of chlorine atoms in the PCl 2 groups in N 3 P 3 Cl 5 NH Pr i . The effects of pressure on the chlorine-35 nuclear quadrupole resonance frequencies of nine chlorine nuclei in similar environments in these two molecules are similar and appear to be characteristic of the functional groups involved.

Chlorine-35 NQR frequencies, ν, for (Cl 3 PN R ) 2 , where R = CH 3 , C 2 H 5 , or Ph, and for (ClOPNCH 3 ) 2 have been measured over the temperature range 77 ⩽ T ⩽ 350 K. Chlorine-35 asymmetry parameters have been measured for (Cl 3 PNCH 3 ) 2 at 295 K, and they show that π-character cannot contribute any more than 1–2% to the nature of the PCl bonds in this molecule. Chlorine-35 NQR frequencies for (Cl 3 PN R ) 2 , where R = CH 3 or Ph, also have been measured over the pressure range 1 ⩽ P ⩽ 1500 Kg cm −2 , at 295 K. These measurements enable three methods to be used to distinguish axial from equatorial chlorine atoms. Their resonance frequencies are different, the temperature coefficients of these frequencies are different, and the pressure coefficients of these frequencies are different. The partial differential coefficients have been evaluated for (Cl 3 PN R ) 2 , where R = CH 3 and Ph. Bayer-type analyses show that the characteristic effects of temperature and pressure on these compounds originate in the typical ionic characters of the PCl bonds and in the characteristic 64 cm −1 PCl 3 torsional-bending modes in these solids. The analyses also indicate that it should be possible to distinguish between different kinds of PCl systems by measuring the effects of applied pressures or changes in temperature on their chlorine-35 NQR frequencies.

Bromine NQR frequencies, v (MHz), for N 3 P 3 Br 6 , N 3 P 3 Br 5 NHPr i and for cis -N 3 P 3 Br 4 (NMe 2 ) 2 have been examined over the temperature range 77⩽=T⩽=300K. Bromine-81 resonance frequencies in these compounds are approximately linearly related Co the chlorine-35 resonance frequencies observed in the corresponding chloro-derivatives: v ( 81 Br) ≈ 8.121 v ( 35 Cl) - 29.4. Bromine nuclei are more sensitive monitors of physical and chemical change than chlorine nuclei. In the cyclotriphosphazatrienes, bromine is more electronegative than amino-nitrogen. Asymmetry parameters for N 3 P 3 Br 6 show that π-character cannot contribute any more than about 0.2% to the nature of the P-Br bonds in this molecule. One phase change, at 125K, has been detected for N 3 P 3 Br 6 and two, at 135K and 215K, for N 3 P 3 Br 5 NHPr i . In cis -N 3 P 3 Br 4 (NMe 2 ) 2 bromine-81 spectra fade out at 215K. Bromine NQR spectra for N 3 P 3 Br 5 NMe 2 have not been detected in the temperature range 77⩽=T⩽=300K. The NQR data enable conformations to be assigned to these molecules.

Chlorine-35 NQR frequencies, v (MHz), in the chlorocyclotriphosphazatrienes are related to the corresponding PC1 bond lengths, d ( A ): d = −0.012 8 v + 2.355. v is also related to θCl, the valence shell electronic population localized on the chlorine atom: θCl = −0.0345v + 8. Chlorine-35 NQR frequencies discriminate between the positional isomers of N3P3C13(NMe2)3. Chlorine-35 NQR frequencies in N1P3Cl6, N3P3Cl5NHPri, N3P3Cl5NC5H10, cis-N3P3Cl4(NMe2)2, and trans-N3P3Cl4(NMe2)2 are linear functions of the applied pressure, P, within the range 1 to 700 kg cm−2. N3P3CI5NC5H10, cis-N3P3Cl4(NMe2)2 and trans-N3P3Cl4(NMe2)2 undergo minor phase changes at about 150 K. The partial differential coefficients (ϖv ϖP) T=293 K′ (ϖv ϖT) P=1kgcm −2 , T=293 K′ and (ϖv ϖT) V,T=293K have been evaluated for each of the resonance frequencies in N3P3Cl6, N3P3Cl5NHPri, N3P3Cl5NC5H10, cis-N3P3Cl4(NMe2)2, and trans-N3P3Cl4(NMe2)2. The pressure derivatives, (ϖv ϖP) T , discriminate between geometric isomers. The temperature derivatives, (ϖv ϖT) , and the pressure derivatives together discriminate between molecular conformers and give detailed information about molecular dynamics in these solids.