| Abstract
| - The first derivatives of catenated cyclotetraphosphinophosphonium cations, [(PhP)4PPhMe]+ (8a),[(MeP)4PMe2]+ (8b), [(CyP)4PPh2]+ (8d), [(CyP)4PMe2]+ (8e), [(PhP)4PPh2]+ (8f), [(PhP)4PMe2]+ (8g), aresynthesized as trifluoromethanesulfonate (triflate, OSO2CF3-) salts through the reaction of cyclopentaphosphines (PhP)5 (4a) or (MeP)5 (4b) with methyl triflate (MeOTf) or by a net phosphenium ion [PR2+, R= Ph, Me; from R2PCl and trimethylsilyltriflate (Me3SiOTf)] insertion into the P−P bond of eithercyclotetraphosphine (CyP)4 (3c) or cyclopentaphosphines (PhP)5 (4a) or (MeP)5 (4b). Although moreconveniently prepared from 4a, compound 8a[OTf] can also be formed from (PhP)4 (3a) and MeOTf, andderivatives 8f[OTf] and 8g[OTf] are also accessible through reactions of 3a and R2PCl/Me3SiOTf with R =Ph or Me, respectively. A tetrachlorogallate salt of [(PhP)4PPhtBu]+ (8c) has been synthesized by alkylationof 4a with tBuCl/GaCl3. 31P{1H} NMR parameters for all derivatives of 8 have been determined by iterativesimulation of experimental data. Derivatives 8a[OTf], 8b[OTf], 8c[GaCl4], 8e[OTf], 8f[OTf], and 8g[OTf]and have been characterized by X-ray crystallography, showing the most favorable all-trans configurationof substituents for the phosphine centers, thus minimizing steric interactions. Each derivative adopts aunique envelope or twist conformation of C1 symmetry. The effective C2 symmetry observed for 8b, d, e,f, and g in solution, signified by their 31P{1H} NMR AA‘BB‘X spin systems, implies a rapid conformationalexchange for derivatives of 8. The core frameworks of the cations in the solid state are viewed as snapshotsof different conformational isomers within the solution-phase pseudorotation process.
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