Deprotonation−Substitution Reactions of Cyclic Methylphenylphosphazenes: Synthesis and Structures of Nongeminal P-Ethyl, P-Phenyl Cyclotriphosphazenes

The deprotonation−substitution reactions of both the cis and trans isomers of nongeminally substituted [(Me)(Ph)PN]3
were investigated. Treatment of the trans isomer, 1, with 3 equiv of n-BuLi followed by 3 equiv of MeI gave only
nongeminal trans-[(Et)(Ph)PN]3, 3, while the same reaction sequence on cis-[(Me)(Ph)PN]3, 2, gave a mixture
of nongeminal di- and trisubstitution products, cis-Et2MePh3P3N3, 4, and cis-Et3Ph3P3N3, 5. These trimers were
separated by column chromatography. No changes in the stereochemistry of the rings occurred during these reactions.
Compound 4 was also prepared using 2 equiv of the reactants and was then converted to 5 by treatment with a
single equivalent of BuLi and MeI. Thermal analysis of the new cyclic trimers indicates that ring-opening polymerization
does not occur and that sublimation occurs at ca. 300 °C. The structures of 4 and 5, obtained by X-ray diffraction,
illustrate the basketlike shape of these molecules with an aromatic bowl formed by the phenyl rings on the top rim,
while the structure of 3 clearly shows the trans orientation of the substituents. Crystal data for trans-Et3Ph3P3N3,
3, at 20 °C are as follows:  C24H30N3P3 monoclinic, a = 14.273(2) Å, b = 9.370(2) Å, c = 19.600(3) Å, β =
107.16(1)°, P21/n, Z = 4. Crystal data for cis-Et2MePh3P3N3, 4, at 20 °C are as follows:  C23H28N3P3, triclinic, a =
10.276(2) Å, b = 10.699(2) Å, c = 11.925(2) Å, α = 72.07(2)°, β = 73.79(1)°, γ = 85.87(1)°, P1̋, Z = 2. Crystal
data for cis-Et3Ph3P3N3, 5, at 20 °C are as follows:  C24H30N3P3 monoclinic, a = 29.488(2) Å, b = 9.8391(1) Å,
c = 21.172(2) Å, β = 126.30(1)°, C2/c, Z = 8.