Studies of phosphazenes. Part 21. Associative and dissociative pathways in the aminolysis reactions of halogenocyclotriphosphazenes
- 1 January 1985
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 2,p. 285-289
- https://doi.org/10.1039/dt9850000285
Abstract
The rates of stepwise replacement of chlorine from hexachlorocyclotriphosphazene (N3P3Cl6) by –NMe2, the last chlorine atom from N3P3(OPh)5Cl by alkylamines, and the first fluorine atom from N3P3F6, by –NMe2, in methyl cyanide, have been determined at three temperatures. Detailed analysis of the kinetic data suggests a concerted SN2(P) mechanism for the first and second Cl substitutions. A sharp changeover from an SN2(P) to an SN1 (P) mechanism occurs at the fourth substitution; the replacement of chlorine from N3P3(OPh)5Cl also occurs by an SN1 (P) pathway. The first F substitution from N3P3F6 by –NMe2 proceeds ca. 20 times slower than the analogous reaction for N3P3Cl6; the kinetic data for these two reactions are in accord with a two-step SN2(P) pathway. Many diverse findings reported for the aminolysis reactions of halogenocyclophosphazenes are explained in terms of the continuous spectrum of mechanisms established in the present study.Keywords
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