Notizen: Beiträge zur Chemie des Phosphors, 46 1.2.3-Triphenyl-cyclo-4.5-carba-1.2.3-triphosphan / 1,2,3-Triphenyl-cyclo-4,5-carba-1,2,3-triphosphane

P–N/P–P Bond Metathesis for the Synthesis of Complex Polyphosphanes

“…The chemical shift of the resonance corresponding to P A (δ(P A ) = −41.8 ppm) is in the expected range for the central P atom of isotetraphosphanes (e.g., (Ph 2 P M ) 3 P A δ(P A ) = −57.2 ppm; THF) . The resonance corresponding to P X in 19 (δ(P X ) = 13.2 ppm) compares well with those reported for P atoms incorporated in a saturated five-membered ring (e.g., P B in all-trans- 1,2,3-triphenyl-1,2,3-triphosphacyclopentane ( 20 ), AB 2 spin system, δ(P A ) = −14.7 ppm, δ(P B ) = 17.2 ppm, 1 J (P A P B ) = 273 Hz) . The 1 J (P A P X ) coupling constant (−258.5 Hz) derived from the fit of the experimental 31 P{ 1 H} NMR spectrum is also comparable to the corresponding coupling in 20 ( 1 J (P A P B ) = 273 Hz).…”

“…Resonances of a characteristic A 2 M spin system (δ(P A ) = 21.2 ppm, δ(P M ) = 63.5 ppm, 1 J (P A P M ) = −277.5 Hz, CD 2 Cl 2 , 300 K) are observed and indicate the all-trans arrangement of the aryl substituents. The chemical shift of P A is comparable to that of the corresponding nuclei in 19 (P X ) and to those of corresponding resonances in related 1,2,3-triphosphacyclopentane derivatives . The resonance corresponding to P M in 24 is shifted to significantly lower field due to the electron-withdrawing effect of the pyrazolyl substituent .…”

“…The magnitudes of the 1 J (P A P X ) and 1 J (P A P Y ) coupling constants ( 1 J (P A P X ) = −269 Hz, 1 J (P A P Y ) = −254 Hz ( rac - 27 c ); 1 J (P A P X ) = −266 Hz, 1 J (P A P Y ) = −255 Hz ( meso - 27 m )) are comparable to those of the aforementioned 1,2,3-triphosphacyclopentane derivatives (compare, for example, 1,2,3-triphenyl-1,2,3-triphosphacyclopentane 1 J (P A P B ) = 273 Hz) . Coupling constants of similar size as the 3 J (P M P M′ ) coupling constant in 27 c,m are observed for other 1,2-bis(phosphanyl)ethane derivatives (e.g., 1-dimethylphosphino-2-diisopropylethane: 3 J (PP) = 25.2 Hz, C 6 H 6 ) .…”

“…The resonances corresponding to the P A and P M nuclei in both diastereomers (δ(P A ) = −41.5 ppm, δ(P M ) = −26.4 ppm ( rac - 27 c ); δ(P A ) = −41.0 ppm, δ(P M ) = −26.9 ppm ( meso - 27 m )) are in the expected range for the corresponding P atoms of isotetraphosphane fragments (vide supra). Similar to hexaphosphane 19 , the resonances corresponding to P X and P Y are observed at lowest field (δ(P X ) = 2.6 ppm, δ(P Y ) = 3.2 ppm ( rac - 27 c ); δ(P X ) = 2.6 ppm, δ(P Y ) = 3.4 ppm ( meso - 27 m )) in the typical region for P atoms incorporated in 1,2,3-triphosphacyclopentane rings. , The observation of three chemically unequal P atoms within each five-membered ring moiety indicates hindered rotation around the P A –P M bond. By analogy with the above discussion of 19 , a twist or a cis–trans conformation of the five-membered rings in solution can be excluded.…”