Cyclotriphosphazenes with geminal (trimethylsilyl)methyl and alkyl or aryl side groups

The synthesis of a series of organosilyl cyclophosphazenes of formula gem-N3P3Cl4(CH2SiMe3)(R), where R = C2H5, i-C3H7, n-C4H9, t-C4H9, neo-C5H11, and C6H5, via organometallic reactions, is described. The chlorine atoms in the cyclic trimers were replaced by trifluoroethoxy groups by reactions that led to either retention of the (trimethylsilyl)methyl units or replacement of them by methyl groups, depending on the reaction conditions. The crystal and molecular structures of gem-N3P3Cl4(CH2SiMe3)(t-C4H9) and the related derivative gem-N3P3Cl4(CH2SiMe3)2 were determined by single-crystal x-ray diffraction methods. Steric hindrance involving the organosilyl units resulting in a widening of the external angle at the supporting phosphorus atom and a narrowing of the corresponding ring angle at that site. Crystals of gem-N3P3Cl4(CH2SiMe3)(t-C4H9) are orthorhombic with space groups Pbca, with a = 14.884 (4) angstrom, b = 15.815 (4) angstrom, c = 16.615 (4) angstrom, V = 3910.9 angstrom 3, and Z = 8. Crystals of gem-N3P3Cl4(CH2SiMe3)2 are monoclinic with space group P21/n, with a = 10.145 (4) angstrom, b = 11.060 (5) angstrom, c = 19.999 (6) angstrom, β = 103.56 (3)degree, V = 2181.4 angstrom 3, and Z = 4. 26 references, 2 figures, 10 tables