Quantitative Determination of Loadings and Oxidation Products of Polystyrene-Bound Phosphines Using ³¹P MAS NMR

Abstract

The use of (31)P magic angle spinning (MAS) NMR for the quantitative determination of resin loadings and the building up of oxidation products was investigated. Loadings of polystyrene-bound phosphines were evaluated via addition of triphenyl phosphate as reference compound. Results for a series of phosphines are consistent with those obtained from well-established analytical methods. The compounds were also investigated with (13)C MAS NMR, and the individual oxidation stabilities were monitored under oxygen atmosphere.

Targeted synthesis of electroactive porous organic frameworks containing triphenyl phosphine moieties

“…These results indicated that the targeted cross-coupling of JUC-Z4 and JUC-Z5 really occurred under the present conditions. 31 P MAS NMR experiments were used to detect the local environment of P atoms. The only one signal at 26.0 ppm shown in the 31 P MAS NMR spectrum of JUC-Z5 can be attributed to the pentavalent P atom in the framework unit (figure 2c).…”

“…31 P MAS NMR experiments were used to detect the local environment of P atoms. The only one signal at 26.0 ppm shown in the 31 P MAS NMR spectrum of JUC-Z5 can be attributed to the pentavalent P atom in the framework unit (figure 2c). After reduction, in addition to the 26 ppm signal, a high-field signal at −8.4 ppm appeared in figure 2d, owing to the formation of trivalent P [31].…”

“…The only one signal at 26.0 ppm shown in the 31 P MAS NMR spectrum of JUC-Z5 can be attributed to the pentavalent P atom in the framework unit (figure 2c). After reduction, in addition to the 26 ppm signal, a high-field signal at −8.4 ppm appeared in figure 2d, owing to the formation of trivalent P [31]. Analysis of the signal intensity shows that ca 33% of original P was reduced.…”

“…The MAS rate was set to 3 -5 kHz. For the 1 H- 13 C cross-polarization (CP)/MAS NMR experiments, the Hartmann-Hahn condition was achieved using hexamethylbenzene (HMB), with a contact time of 2.0 ms and a repetition time of 2.0 s. 31 P single-pulse experiments were performed with a 3.8 µs pulse width (π/2) and a 20 s recycle delay. The chemical shifts of 13 C and 31 P were referenced to HMB and an aqueous solution of H 3 PO 4 (1 M).…”