The equation 7 1 + 11 PCl 3 Η 2 7 + 11 + 21 HCl describes 1,2-diphospholides and 1,2,4-triphospholides. The cation of the ionic oxidation product 7 has a phenalene structure with in part the reaction of allylidenetriphenylphosphorane (triphenylphosphonium allylide) 1 with PCl 3 . It involves the three peripheric PCl ring members and a chlorophosphonium center. In the crystal two of these bowl-shaped cations substitution of all Ξ±and Ξ³-hydrogen atoms of 1 and a concomitant disproportionation of the phosphorus. The encapsulate a chloride anion. This is shown by an X-ray structure investigation. The structure of other products is reduction product 11 and its less highly substituted precursor 9 are new examples of the favoured family of 3-phosphonio elucidated by 31 P-NMR spectroscopy.
Reaction and Products Allylidenetriphenylphosphorane
[(prop-2-enediyl)triphenylphosphorane] (1) may be understood as phosphoniosubstituted allyl anion and is expected to exhibit the reacti-
The reaction of phosphorus trichloride with 1 in pyridine at 0Β°C was visually observable. 31 P-NMR spectroscopy was vity of an asymmetric allyl anion [1] [2] [3] [4] .
used to monitor several experiments with different molar ratios. The spectra always indicated complex mixtures of products. These mixtures at room temperature continued to change their composition for a long time (up to several months). At long reaction times the spectra tended to become simpler. Naturally the reaction of the three-functional PCl 3 with the three-functional partner 1 can be expected to With phosphorus trichloride it consequently may interact at its Ξ±-or Ξ³-carbon atom leading to compounds 2 or 3 as take various pathways with numerous intermediates. In the course of the reaction more and more of the functions are the primary substitution products and it also may interact at both sites with the same PCl 3 molecule or with two dif-used, and the number of alternatives should decrease.
With a 3:1 initial molar ratio of 1 and PCl 3 , compound 7 ferent of them to give compounds 4 or 5 as secondary products. All in all there are three hydrogen atoms of 1 that can becomes the main product after 2 d. Its identity follows from its 31 P{ 1 H}-NMR spectrum of [AB] 3 D type. As only be substituted. The different alternatives of this reaction were considered earlier [5] . The actual experiment (in ben-the two-bond coupling constants J AB and J BD , and the four-bond coupling constant J AD are large enough to influ-zene with an excess of 1) gave a product which was assumed to be the hydrochloride of the "tris-ylene" 6. It would be ence the signal splitting significantly (J AAΠ , J ABΠ and J BBΠ are too small), the spectrum is rather simple in appearance the result of the substitution of three molecules of 1 exclusively at the Ξ³-position by the same PCl 3 molecule. Com-(Figure 1). The chemical shifts Ξ΄ A , Ξ΄ B and Ξ΄ D are in the expected range, Ξ΄ D in particular is characteristic for a chlo-pound 6 was obtained from its hydrochloride by reaction with sodium amide. It is described as a deep red, very reac-rophosphonium center (Table 1).
No intermediate on the way to 7 could be identified from tive, air-sensitive substance.
We repeated the reaction of 1 with PCl 3 in pyridine, the spectra. In particular compound 6 (or its hydrochloride) was not found; however, it cannot be excluded as an inter-which in similar cases had proved as a convenient solvent, able to take up the hydrogen chloride lost from the reaction mediate either. It would be expected to possess a highly reactive phosphane center which easily becomes oxidized. partners in the substitution reaction [6] .