Kinetisch kontrollierte Protonierung eines cyclischen Phosphamethanidkomplexes zum PH-Phosphoniumylid

Synthesis of Phosphorus Ylides Bearing a PH Bond from a Kinetically Stabilized 1,3,6‐Triphosphafulvene

“…In the 31 P NMR spectrum of 5 , the peak at δ P =−23.2 ( 5 a ) or −4.5 ppm ( 5 b ) is accompanied by a considerably large J (P,H) coupling constant. These J (P,H) constants are close to the corresponding data of the reported phosphorus ylides with PH bonds 6–8. In the 13 C NMR spectrum of 5 a , one of the sp 2 ‐carbon atoms in the C 3 P 2 ring that connects with the phosphorane moiety was observed at relatively higher field ( δ C =119.8 ppm) than the other two carbon atoms ( δ C =182.6 and 171.4 ppm).…”

“…To study the regioselective protonation of 3 , we calculated the molecular electrostatic potential (MEP, visualized with the gOpenMol program22) maps of the anion 10 and its lithium complex (Figure 3). According to these results, in the case of the pure anion 10 (Figure 3a), the protonation is favored mainly on the ring, while in the lithium complex (Figure 3b) the exo ‐phosphorus atom is the main protonation side, which clearly shows the role of the kinetic effects in the formation of 5 8. Thus, the lithium atom plays an important role in the reactivity of 3 .…”

“…In the case of phosphorus ylides bearing a PH bond, the activation energy is small and thus they should be easily isomerized 24. The stability of 5 and 7 might be attributed to the π‐accepting effect of the PC moiety16, 17, 25 which prevents H‐migration 8. Additionally, the NICS value of 8 (−10.7 a.u.)…”

“…6 An alternative approach to synthesize phosphorus ylides with a PH bond was demonstrated by Bertrand and co‐workers who utilized bulky diisopropylamino groups and the PCP skeleton for the preparation of phosphorus ylides bearing PH bonds ((R 2 N) 2 PHCPX(NR 2 ) 2 ; X=H or F, R= i Pr) 7. Recently, Niecke and co‐workers have succeeded in isolating cyclic phosphorus ylide C where trimethylsilyl groups and pyridyl groups stabilize the >P(H)C< system 8…”

Theoretical Study on Novel Mixed Valence, P‐H Functional P‐Ligands, and Their Tautomerization

“…In this context, the existence of tautomeric forms III of PH derivatives II , i.e., possessing more classical phosphane structures with E–H units, and/or their equilibria had attracted particular interest. Especially, the tautomeric pairs IIa/IIIa and IIb/IIIb had been intensely studied with respect to substituent effects, and the stabilizing effect of electron‐withdrawing groups on the P–H tautomer together with a great steric demand of P‐substituents was recognized .…”