KINETICS AND MECHANISM OF THE REACTION BETWEEN OLIGOSILOXANES AND P-TRICHLORO-N-DICHLOROPHOSPHORYL MONOPHOSPHAZENE (Cl3P[dbnd]N-POCl2) |
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| Authors: | Abdeslam Meliani Yann Vaugeois Hamza Bali Ahmed Mazzah Roger de Jaeger Jean Habimana |
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| Affiliation: | 1. Laboratoire de Spectrochimie lnfrarouge et Roman , CNRS, UMR Université des Sciences et Technologies de Lille , 8516, B[acaron]t. C5, Villeneuve d'Ascq, France;2. UFR Chimie des Matériaux, Luboratoire de Chimie Minérale, Faculté des Sciences et Techniques Fès-Sa?ss , Université Sidi Mohamed Ben Abdellnh , Fès, Morocco;3. Laboratoire de Spectrochimie lnfrarouge et Roman , CNRS, UMR Université des Sciences et Technologies de Lille , 8516, B[acaron]t. C5, Villeneuve d'Ascq, France;4. Dow Corning S.A. Parc Industriel , Zone CB, 7180, Seneffe, Belgium |
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| Abstract: | Abstract 31P NMR investigation has been made of the action of Cl3P[dbnd]N-POCl2(I) first on hexamethyldisiloxane (Me3Si)2O and then on oligosiloxanes Me3Si-(OSiMe2)n-OSiMe3 n = 2 and n=3. The reactions were carried out in bulk or in solution with molar ratios siloxane/(I) varying from I to 5. It was demonstrated that only the monosubstitution of a chlorine atom by the -(OSiMe2)n,-OSiMe3 species n = 0, 2, 3 with elimination of trimethylchlorosilane occurred leading to the derivatives Cl2OP-N[dbnd]PCl2O(SiMe2-O)nSiMe3 (II). For n=2, 3 the siloxane redistribution reactions were observed by 29Si NMR analysis. A two steps mechanism is proposed. consisting in a nucleophilic substitution, involving a tricoordinate phosphazenium intermediate, followed by the formation of an active ionic centre probably an oxonium ion, arising from the solvatation by the siloxane of this phosphazeniurn ion and /or of (II) leading to the redistribution reactions. The influences of the solvent, of trimethylchlorosilane, of the temperature, and of the addition of a protonated species (MDH) were investigated. |
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| Keywords: | Chlorophosphazenes Siloxane Redistribution Reactivity Mechanism |
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