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-Et(2)MePh(3)P(3)N(3), 4, and cis-Et(3)Ph(3)P(3)N(3), 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 degrees 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-Et(3)Ph(3)P(3)N(3), 3, at 20 degrees C are as follows: C(24)H(30)N(3)P(3) monoclinic, a = 14.273(2) A, b = 9.370(2) A, c = 19.600(3) A, beta = 107.16(1) degrees, P2(1/n), Z = 4. Crystal data for cis-Et(2)MePh(3)P(3)N(3), 4, at 20 degrees C are as follows: C(23)H(28)N(3)P(3), triclinic, a = 10.276(2) A, b = 10.699(2) A, c = 11.925(2) A, alpha = 72.07(2) degrees, beta = 73.79(1) degrees, gamma = 85.87(1) degrees, P1, Z = 2. Crystal data for cis-Et(3)Ph(3)P(3)N(3), 5, at 20 degrees C are as follows: C(24)H(30)N(3)P(3) monoclinic, a = 29.488(2) A, b = 9.8391(1) A, c = 21.172(2) A, beta = 126.30(1) degrees, C2/c, Z = 8.
Jung
June-Ho
JH
Department of Chemistry, Southern Methodist University, Dallas, Texas 75275-0314, USA.
Zhang
Hongming
H
Wisian-Neilson
Patty
P