A Novel Synthesis of Hexakis(trifluoromethyl)cyclotriphosphazene. Single-Crystal X-ray Structures of N 3 P 3 (CF 3 ) 6 and N 3 P 3 F 6 Rajendra Prasad Singh, Ashwani Vij, Robert L. Kirchmeier, and Jean’ne M. Shreeve* Department of Chemistry, University of Idaho, Moscow, Idaho 83844-2343 ReceiVed August 13, 1999 Reaction of hexafluorocyclotriphosphazene (N 3 P 3 F 6 ) with trimethyl(trifluoromethyl)silane in the presence of a catalytic amount of cesium fluoride in THF produced hexakis(trifluoromethyl)cyclotriphosphazene [N 3 P 3 (CF 3 ) 6 ] in 90% isolated yield. N 3 P 3 (CF 3 ) 6 is fully characterized by melting point, IR, NMR ( 19 F, 13 C, 31 P), MS, and elemental analysis data. Single-crystal X-ray structures of N 3 P 3 (CF 3 ) 6 and N 3 P 3 F 6 are reported. Introduction Phosphazenes are an important class of compounds, and their chemistry is well documented in the literature. 1 However, primarily because of the difficulties encountered in their syntheses, fluoroalkyl-substituted phosphazenes have not been studied in detail. Fluoroalkyl-substituted phosphazenes are expected to possess useful properties, e.g., as fire retardants. Moreover, the fluoroalkyl group should decrease the flammabil- ity of the phosphazene as compared to nonfluorinated alkyl and aryl derivatives. Hexakis(trifluoromethyl)cyclotriphosphazene [N 3 P 3 (CF 3 ) 6 ], 1, is a promising compound, but its synthesis in the laboratory in good yield has not previously been achieved. The only successful preparation of 1 reported 2 involved a low- yield (12%) cyclization reaction of (CF 3 ) 2 P(Cl 2 )NH 2 with triethylamine as shown in Scheme 1. Recently, we and others carried out nucleophilic trifluoro- methylation of various substrates by using trimethyl(trifluo- romethyl)silane (TMS-CF 3 ) in the presence of fluoride ion initiators (e.g., KF, (TBA)F, and CsF). 3 By using this methodol- ogy, we can now report the synthesis of 1 in excellent isolated yield. Results and Discussion Reaction of 2 4 with 7 equiv of TMS-CF 3 in tetrahydrofuran (THF) at 70 °C in the presence of catalytic amounts of anhydrous cesium fluoride led to the nearly quantitative formation of 1 (Scheme 2) on the basis of 19 F and 31 P NMR spectra. To recover compound 1 free of cesium fluoride and THF, the reaction mixture was cooled to -100 °C, which caused components soluble in THF to precipitate. After the THF was decanted at low temperature, the product was agitated vigorously with chloroform at room temperature and the mixture was cooled to -50 °C. The chloroform that contained some residual THF was further decanted at low temperature. This process was repeated once more with chloroform. Finally, the pure product was obtained in 90% yield by low-temperature trap-to-trap distillation. On the basis of spectroscopic data, no other substitution products or ring-opened phosphazenes were ob- served. Although this separation procedure seems a bit cumber- some, fractional condensation cannot be used because of the ease with which 1 is sublimed. Compound 1 has been characterized previously 2 by melting point, IR, and elemental analysis data and by a molecular weight determination. We have observed the same melting point and IR data for 1 and have also characterized this compound by 19 F, 31 P, 13 C NMR, MS, and single-crystal X-ray analysis. The 19 F NMR spectrum showed a doublet at δ -73.6 with a J P-F coupling constant of 130 Hz, indicating magnetically equivalent trifluoromethyl (CF 3 ) groups. The 31 P NMR spectrum showed a well-resolved septet at δ 3.1 with a J P-F coupling constant of 130 Hz. The 13 C NMR spectrum appears as a doublet of quartets at δ 118.8 with coupling constants of J C-P ) 150 Hz and J C-F ) 290 Hz. In the mass spectrum (electron impact, EI), the parent ion was observed at m/z 549 (1% relative intensity). The base peak due to M + - CF 3 was observed at m/z 480. Compound 1 was found to have a vapor pressure of ∼0.25 Torr at 22 °C. * Corresponding author. Tel: 208-885-6651. Fax: 208-885-6198. E- mail: jshreeve@uidaho.edu. (1) (a) Ratz, R.; Schroeder, S.; Ulrich, H.; Kober, E.; Grundmann, C. J. Am. Chem. Soc. 1962, 84, 551-555. (b) Shaw, R. A.; Keat, R.; Hewlett C. In Phosphazene Compounds in PreparatiVe Inorganic Reactions; Jolly, W. L., Ed.; Interscience: New York, 1965; Vol. 2, pp 1-91. (c) Allcock, R. Phosphorus-Nitrogen Compounds; Academic Press: New York, 1972. (d) Allen, C. W. J. Fire Sci. 1993, 11, 320-328. (2) Tesi, G.; Douglas, C. M. J. Am. Chem. Soc. 1962, 84, 549-551. (3) (a) Patel, N. R.; Kirchmeier, R. L. Inorg. Chem. 1992, 31, 2537- 2539. (b) Singh, R. P.; Kirchmeier, R. L.; Shreeve, J. M. J. Org. Chem. 1999, 64, 2579-2681. (c) Singh, R. P.; Cao, G.; Kirchmeier, R. L.; Shreeve, J. M. J. Org. Chem. 1999, 64, 2873-2876. (d) Singh, R. P.; Vij, A.; Kirchmeier, R. L.; Shreeve, J. M. J. Fluorine Chem. 1999, 98, 127-132. (e) Singh, R. P.; Kirchmeier, R. L.; Shreeve, J. M. Org. Lett. 1999, 1, 1047-1049. (f) Prakash, G. K. S.; Yudin, A. K. Chem. ReV. 1997, 97, 757-786. (g) Prakash, G. K. S. In Synthetic Fluorine Chemistry; Olah, G. A., Chambers, R. D., Prakash, G. K. S., Eds.; John Wiley & Sons: New York, 1992; pp 227-246. (4) Schmutzler, R. Inorg. Synth. 1967, 9, 76-78. Scheme 1 Scheme 2 375 Inorg. Chem. 2000, 39, 375-377 10.1021/ic9909781 CCC: $19.00 © 2000 American Chemical Society Published on Web 12/31/1999