Fluoride Ion Induced Reactions of Silicon−Oxygen and Silicon−Sulfur Bonds with Hexafluorocyclotriphosphazenes:  Synthesis, Reactivity, and X-ray Structural Analyses of Sulfur/Oxygen-Containing Monospirofluorophosphazenes<sup>,</sup> (1996)

Bifunctional trimethylsilyl ethers/thioethers/dithioethers react readily with N3P3F6 in the presence of a catalytic amount of CsF in THF to yield spirofluorophosphazenes or dangling or bridged fluorophosphazenes with concomitant elimination of Me3SiF. With sulfur-containing aliphatic bifunctional reagents of the type Me3SiX(CH2)nSSiMe3, five- and six-membered monospirofluorophosphazenes, N3P3F4[X(CH2)nS] [X = O or S; n = 2 or 3] (1−4), are formed in good yield. Crystals of N3P3F4[OCH2CH2S] (1) are monoclinic, P21/c; fw = 287.05, a = 8.727(10) Å, b = 11.246(2) Å, c = 9.787(2) Å, β = 100.91(10)°, V = 943.2(3) Å3, and Z = 4. N3P3P4[OCH2CH2CH2S] (2) is orthorhombic, Pbca; fw = 301.08, a = 12.399(4) Å, b = 10.105(2) Å, c = 16.787(2) Å, V = 2103.3(9) Å3, Z = 8. N3P3F4[SCH2CH2S] (3) is triclinic, P1̄; fw = 303.11, a = 9.501(2) Å, b = 9.764(3) Å, c = 11.092(5) Å, α = 74.97°, β = 88.03°, γ = 85.85°, V = 991.0(6) Å3, and Z = 2. N3P3F4[SCH2CH2CH2S] (4) is orthorhombic, Fdd2; fw = 317.14, a = 18.238(4) Å, b = 41.390(8) Å, c = 5.965(12) Å, V = 4503(2) Å3, and Z = 16. The 31P NMR spectra of these derivatives show a large dependence on the ring size and an attempt is made to explain this observation on the basis of structural parameters. Reactions of N3P3F6 with disiloxanes such as (Me3SiOCH2CH2)2O at temperatures below 80 °C yield only the dangling product 5a. When the reaction temperature is elevated to ∼110 °C, an oily liquid that is identified as the bridged fluorophosphazene (N3P3F5OCH2CH2)2O (5b) is isolated. When [Me3SiOC(CF3)2]2C6F4 acts as a bifunctional reagent, a totally fluorinated bridged phosphazene, [N3P3F5OC(CF3)2]2C6F4 (6), forms at ∼65 °C. Aromatic disiloxanes are very facile reagents for the formation of spirocyclic products when N3P3F6 is reacted under mild conditions with the bis(trimethylsilyl) ethers of 1,2-catechol, 3-fluoro-1,2-catechol, 2,3-naphthalenediol, and 2,2‘-biphenol. No ring degradation is observed with 3-F-1,2-C6H3(OSiMe3)2 and 1,2-C6H4(OSiMe3)2, which give the monospiro derivatives N3P3F4[3-F-1,2-C6H4O2] (7) and N3P3F4[1,2-C6H4O2] (8a) in good yields as well as the dispirophosphazene derivative N3P3F2[1,2-C6H4O2]2 (8b). Crystals of 8a are orthorhombic Imma; fw = 319.03, a = 7.4642(5) Å, b = 9.5108(7) Å, c = 16.2807(12) Å, V = 1155.78(14) Å3, and Z = 4; 8b is monoclinic, P21/n; fw = 389.12, a = 10.015(10) Å, b = 5.612(10) Å; c = 27.818(4) Å, β = 96.70°, V = 1552.8(4) Å3, Z = 4. N3P3F4[2,3-C10H6O2] (9a) is monoclinic, P21/c; fw = 369.09, a = 11.291(2) Å, b = 17.139(3) Å, c = 7.183(10) Å, β = 101.68°, V = 1361.2(4) Å3, Z = 4; N3P3F4[2,2‘-C12H8O2] (10) is monoclinic C2/c; fw = 395.12, a = 24.932(5) Å, b = 7.930(10) Å; c = 18.875(4) Å, β = 124.55°, V = 3073.6(10) Å3, Z = 8. The residual fluorine atoms on the phosphazene rings in 7, 8a, 9a, and 10 can be substituted by fluorophenoxy groups on reaction with the corresponding o-, m-, or p-(trimethylsilyl)phenoxy ether to give fully substituted phosphazenes of the type N3P3X(OC6H4F)4 [X = 3-F-1,2-C6H3O2 (11), 1,2-C6H4O2 (12), 2,3-C10H6O2 (13−15), and 2,2‘-C12H8O2 (16−18)]. Crystals of N3P3[2,2‘-C12H8O2](p-FC6H4O)4 (18) are triclinic P1̄; fw = 763.49, a = 10.597(2) Å, b = 12.121(2) Å, c = 15.324(3) Å, α = 70.38°, β = 84.53°, γ = 65.77°, V = 1688.6(5) Å3, and Z = 2. The N3P3 core in 18 is distorted and the two biphenoxy rings are twisted at 46.1°.