Lithium Salts of 2,4,6‐Triaryl‐λ⁴‐phosphinine Anions – A Comparison Study

Abstract

The λ 3 -phosphinine derivatives 2,6-diphenyl-4-(p-tolyl)phosphinine and 2-(2Ј-pyridyl)-4,6-diphenylphosphinine were quantitatively converted into the corresponding λ 4 -phosphinine anions by reaction with phenyllithium. Systematic hydrolysis experiments with H 2 O and MeOH show that a subtle interplay between the pK a values of the generated 1,2-dihydrophosphinine derivatives and the pK b value of the formed bases, LiOH and LiOCH 3 , respectively, leads either to the kinetic or thermodynamic product. The coordination[a]

Recent Developments in the Chemistry of Pyridyl-functionalized, Low-coordinate Phosphorus Heterocycles

“…Nevertheless, it turned out that hexafluoro-2-butyne indeed reacts cleanly to the fluorinesubstituted phosphabarrelene 10 (Scheme 3). 35 Figure 10 depicts the crystallographic characterization of 10 along with the corresponding 31 P{ 1 H} NMR spectrum, confirming that the cycloaddition of the alkyne occurs exclusively in the 1,4-position. The structural analysis revealed a strong pyramidalization at the phosphorus atom (¾(CPC) = 281.45°), which reflects a more pronounced s character of the phosphorus lone pair compared with the situation in PPh 3 (PPh 3 : ¾(CPC) = 308.8°).…”

“…24 As expected, 5 can be converted easily into the corresponding λ 4 σ 3 -phosphinine species 11 by reaction with stoichiometric amounts of PhLi in THF at T = ¹78°C (Scheme 4). 37 A large chemical shift is observed by 31 P{ 1 H} NMR spectroscopy on going from the neutral phosphinine (¤ = 187.4 ppm) to the anionic form (¤ = ¹58.6 ppm). This indicates that the aromaticity in the ring has been disrupted substantially owing to the presence of a rather basic phosphorus center with a formal sp 3 hybridization (PMe 3 :…”

Reactivity of Aromatic Phosphorus Heterocycles – Differences Between Nonfunctionalized and Pyridyl‐Substituted 2,4,6‐Triarylphosphinines

“…However, when trifluoromethanesulfonic acid was reacted with the pyridyl-substituted phosphinine 2, a new resonance at δ = +189.0 ppm appeared in the 31 …”

“…Phosphinines undergo only slow oxidation with sulfur under rather harsh reaction conditions. [23] The conversion of 1 and 2 was followed by 31 Interestingly, the pyridyl-functionalized phosphinine 2 reacted quantitatively to form the corresponding phosphinine sulfide 6 within 18 h at T = 90°C (Scheme 3 and Figure 5, blue line). To investigate the influence of the pyridyl group on the oxidation process, we added a slight excess of pyridine to the nonfunctionalized phosphinine 1.…”

“…Thus, a small amount of methanol was added to a solution of 5 in dichloromethane at room temperature, and the reaction was investigated by 31 Next, we investigated the reaction of the pyridyl-functionalized phosphinine sulfide 6 with methanol in dichloromethane at room temperature. Much to our surprise, of the five possible compounds/diastereoisomers, the reaction led almost exclusively to a single product, characterized by a resonance in the 31 P{ 1 H} spectrum at δ = 61.2 ppm (Figure 9, a).…”