Stable phosphinous acids

The Influence of Electron‐Withdrawing Groups on the Chemistry of Phosphorus: Tautomerization of Bis(s‐triazinyl)phosphanes

“…The tautomeric equilibrium between 3 a and 4 a is related to both the ketoenol tautomerism observed for diacylphosphanes [9] and the isomerization of bis(benzothiazol-2-yl)phosphane, which exists both in the solid state as well as in diethyl ether solution as its NÀH isomer. Surprisingly, the PÀH isomer of the bis(benzothiazol-2-yl) derivative HP(bth) 2 , although it is detectable in THF solution by NMR spectroscopic methods, is instable and dismutates into P(bth) 3 and H 2 P(bth). [10] This behavior was not observed for the s-triazine derivatives 3 a and 4 a,.…”

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The influence of electron-withdrawing groups in phosphorus chemistry is essential, for example for the realization of organic electron-conducting materials [1] and chiral p-acidic phosphane ligands [2] as well as for the stabilization of phosphinous acids [3] and low-valent phosphorus species. [4,5] 1,3,5-Triazin-2-yl groups (referred to in the following as striazinyl) are strongly electron-withdrawing substituents.

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“…(2)], leading to the formation of the corresponding phosphinous acids R 2 POH, which exist in a solvent-dependent equilibrium with the tautomeric phosphane oxides R 2 P(O)H (R = C 6 F 5 , p-C 5 NF 4 ). [3] Instead of the expected nucleophilic substitution of one striazinyl group by an OH group, the hydrolysis of tris(striazinyl)phosphanes 2 proceeds by a nucleophilic attack of a hydroxide ion at the ipso carbon atom of one s-triazinyl ring, resulting in the formation of the novel bis(s-triazinyl)phosphanes 3 [Eq. (3)].…”

Tetrakis[2,4‐bis(trifluormethyl)phenyl]diphosphoxan – das Anhydrid einer Phosphinigsäure

“…[3] Die ursprünglich [4] als Bis(pentafluorphenyl)phosphinigsäure, (C 6 F 5 ) 2 POH, beschriebene Verbindung liegt sowohl im Festkörper als auch in CHCl 3 -, Toluol-oder CH 3 CN-Lösung ausschließlich als Phosphanoxid vor. [5] Das Phosphinigsäure-Tautomer kann nur in Lösungsmitteln mit hoher Donorzahl (z. B. DMF, THF) beobachtet werden.…”

“…[5] Stärker elektronenziehende Substituenten als die C 6 F 5 -Gruppe, z. B. die p-Tetrafluorpyridyl-Gruppe, [6] bewirken eine weitergehende Stabilisierung des Phosphinigsäure-Tautomers, [5] während ein zunehmender Raumbedarf (z. B. bei der 2,4-Bis(trifluormethyl)phenylgruppe, 2,4-(CF 3 ) 2 C 6 H 3 ) die PhosphanoxidStruktur begünstigt.…”