Synthesis of a new class of fused cyclotetraphosphazene ring systems.

Octachlorocyclotetraphosphazene (1) was reacted with butylamines [n-butyl, i-butyl, sec-butyl, and t-butyl] in a 1:0.8 mol ratio in THF to obtain cyclotetraphosphazenes bearing a P-NH group, N4P4Cl7(NHR) [R = n-butyl (2a), i-butyl (2b), sec-butyl (2c), t-butyl (2d)](2a-d). The cyclotetraphosphazene derivatives 2a, 2b, and 2c were treated with sodium hydride giving rise to a new type of cyclophosphazene compounds (P8N8 ring) consisting of three fused tetramer rings (3a-c). Whereas reaction of sodium hydride with the t-butylaminocyclophosphazene derivative (2d) gave a P-O-P bridged compound (4) presumably as a result of hydrolysis reaction associated with moisture in the solvent. It is likely that the 16-membered cyclooctaphosphazene derivatives (3a-c) are formed by a proton abstraction/chloride ion elimination, intramolecular nucleophilic attack, ring opening and intermolecular condensation processes, respectively.

Nucleophilic substitution reactions of 10- and 11-membered fluorodioxy ansa cyclotriphosphazene derivatives.

The reactions of cyclophosphazenes with 10-membered ansa-{N3P3Cl4[OCH2(CF2)3CH2O] (1a)} and 11-membered ansa-{N3P3Cl4[OCH2(CF2)4CH2O] (1b)} rings with the sodium salts of methanol in a THF solution at different molar ratios were used to investigate the reaction pathways and mechanism of nucleophilic substitution at the PCl2 and PCl(OR) phosphorus atoms. The reactions afforded eleven products, whose structures have been characterized by elemental analysis, mass spectrometry, (1)H, (19)F and (31)P NMR spectroscopy and X-ray crystallography; mono-methoxy derivatives (2a, 3a, 3b), di-methoxy derivatives (5a-7a, 5b), tri-methoxy derivatives (8a, 8b) and the tetra-methoxy derivatives (9a, 9b). The X-ray crystallographic studies of four compounds (6a-8a and 8b) demonstrated unambiguously that nucleophilic substitution reactions at the ansa-ring PCl(OR) phosphorus atoms of the cyclotriphosphazene compounds N3P3Cl4[OCH2(CF2)nCH2O] n = 3 (1a) and 4 (1b) occurred with a retention of configuration for both the 10- and 11-membered fluorodioxy ansa rings, respectively. The results confirmed that the reactions with 1a containing the 10-membered ansa-ring occurred competitively at both the PCl2 and P(OR)Cl moieties with an approximate 8 : 1 preference at the PCl2 group, whereas reactions with 1b containing the 11-membered ansa-ring occurred exclusively at the PCl2 group before the P(OR)Cl moiety. The results were mainly rationalized in terms of the P-Cl bond lengths of the reactants and the cation-assisted mechanism of reaction.