Preparation, spectral characterization, and single crystal X-ray structures of cis and trans isomers of 2,4,6-trifluoroethoxy-1,3,5-triethyl-1,3,5,2 $\lambda^6$, 4 $\lambda^6$, 6 $\lambda^6$-triazatriphosphorinane-2,4,6-trioxide, $[ETNP(O)(OCH_2CF_3)]_3$

Oxidation of the cis isomer of the $\lambda^3$ -cyclotriphosphazane $[EtNP(OCH_2CF_3)]_3$ with trimethylamine-N-oxide (TMNO) gives the cis isomer of trioxo- $\lambda^5$-cyclotriphosphazane $[EtNP(OCH_2CF_3)]_3$; the trans isomer of $[EtNP(OCH_2CF_3)]_3$ is obtained by the treatment of a cis and trans mixture of $[EtNP(OCH_2CF_3)]_3$ with aqueous H2O2. The two trioxocyclotriphosphazanes have been characterized by elemental analysis, IR, and NMR (1H, 13C, 19F, and 31P) spectroscopy. The solid state structures of both the isomers have been determined by single crystal X-ray diffraction. The six-membered P3N3 ring in both the isomers exhibits a twist-boat conformation; in the cis isomer, the trifluoroethoxy substituents lie on the same side of the ring, whereas, in the trans isomer, two trifluoroethoxy groups are on one side of the ring and the third on the other side of the ring. Crystal data for cis$[EtNP(OCH_2CF_3)]_3$ : monoclinic, $P2_1/n$, a = 13.593(3), b = 9.721(2), c = 17.539(3) Ã, \beta = 99.49(2)Ã, V = 2286(1) $A^3$, Z = 4, and Final R = 0.047. Crystal data for trans-$[EtNP(OCH_2CF_3)]_3$: monoclinic, P21/n, a = 11.685(4), b = 15.115(5), c = 13.233(5) Ã, - = 102.21(3), V = 2284(1) $A^3$, Z = 4, and Final R = 0.078