Structural and ³¹P NMR solution studies on some cyclic triphosphenium ions and their 2‐arsa‐analogues

The identification of some novel four‐membered ring cyclic triphosphenium ions in solution

“…For the systems where comparison is possible, there is a marked shift of the P A resonance to higher frequency on going from the five-to the four-membered ring (58.8 ppm for methyl and 75.8 ppm for cyclohexyl), while the P B signal moves to slightly lower frequency (by 38.6 and 42.4 ppm, respectively). The only mildly surprising feature of the results is that 1 J PP for 1 is slightly higher than that for its five-membered ring analogue [7], whereas 1 J PP for 2 is markedly lower and is comparable with the values for the species with nitrogen substituents on the outer P atoms [10]. This difference in behavior presumably arises from variations in the electron distribution.…”

“…The 31 P NMR data for 1, 2, and 3 are listed in Table 1, together with results for the two previously reported cationic four-membered rings with nitrogen substituents on P B [10], and for the corresponding five-membered ring cyclic triphosphenium ions with methyl [7] or cyclohexyl substituents on P B . For the systems where comparison is possible, there is a marked shift of the P A resonance to higher frequency on going from the five-to the four-membered ring (58.8 ppm for methyl and 75.8 ppm for cyclohexyl), while the P B signal moves to slightly lower frequency (by 38.6 and 42.4 ppm, respectively).…”

Protonation of some cyclic triphosphenium ions

“…2(b). The P P bond distance is thus expected to increase to a normal single bond length, instead of being intermediate between P P single and P P double bond lengths, as found in all crystal structures of cyclic triphosphenium ions ascertained to date [1,7,8]. None of the protonated derivatives has yet been isolated in a crystalline state, so this prediction remains unconfirmed at present.…”

“…Small amounts of oxidation products such as the diphosphane monoxide, which gives rise to two doublets, or the diphosphane dioxide, which gives a single resonance, were occasionally detected, particularly for diphosphanes with alkyl substituents, but these did not interfere with formation of the cyclic triphosphenium ions. These were prepared quantitatively in CH 2 Cl 2 solution as described previously [7,8,10,11], from either a 3:2 mixture of the diphosphane and PCl 3 , or a 1:1:1 mixture of the diphosphane, PCl 3 , and SnCl 2 , where the hexachlorostannate(IV) was required. The calculated quantity of a solution of AlCl 3 and t BuCl (1:1) in CH 2 Cl 2 or of triflic acid was added by microsyringe, once formation of the ring had been confirmed spectroscopically.…”

Crystal and molecular structures of some six‐coordinate tin(IV) halogeno complexes with phosphorus‐containing ligands

“…During our investigations into new phosphorus heterocycles such as cyclic triphosphenium ions [1][2][3][4][5][6][7] and their P-alkyl or -aryl derivatives [8][9][10][11], we have often used tin(II) halides SnX 2 (X Cl or Br) as reducing agents, in an attempt to obtain crystalline products as hexahalogenostannates(IV). Occasionally, we have instead obtained crystalline tin-containing coordination complexes, sometimes in the presence of adventitious oxygen and/or moisture, resulting in the coordination by O donors and/or protonation of one of the phosphorus atoms in a diphosphane.…”