Novel phosphazene derivatives: Synthesis, anisochronism and structural investigations of mono- and ditopic spiro-crypta phosphazenes

The reactions of hexachlorocyclotriphosphazatriene, N3P3Cl6, with N2O2-donor type coronands (diaza-crown ethers) 1-3 afford novel monotopic 4-7 and ditopic 8-10 spiro-crypta phosphazenes, respectively. It has been observed that the reactions of N3P3Cl6 with 1 equivalent amount of coronands 1-3 yield only monotopic spiro-derivatives, while three equivalent amount of coronands 2 and 3 give dominantly ditopic dispiro-crypta-phosphazene skeletons. On the other hand, the 31P NMR spectrum of 8 indicates that the ditopic spiro-ansa phosphazene 10 is present besides the ditopic dispiro derivative 8. Unexpectedly, the reaction of 6 with excess amount of pyrrolidine leads to the formation of geminal product 7. The 31P NMR spectra of 4, 5, 6 and 10 indicate that all of these compounds have anisochronism. The structures of 5, 8 and 9 have been determined by X-ray crystallography. The relative radii of macrocyclic hole sizes of 5, 8 and 9 are calculated from the crystallographic results. The relationships between the exocyclic NPN and endocyclic NPN bond angles of the analogous compounds with δP-shifts of NPN phosphorus atoms have been discussed. Thus, sums of the bond angles around the nitrogen atoms are in the range of [342.7(2)°-354.4(2)°], showing that the nitrogen atoms have pyramidal configurations. The pyramidal configuration gives rise to stereogenic properties. The salient spectroscopic features [FTIR, 1H, 13C, 31P NMR, HETCOR (for 5 and 7) and MS] of all the compounds are presented.