Properties of Cyclic Phosphazenes

The temperature dependence of the electrical resistivity of a variety of halogenocyclophosphazenes and their derivatives has been measured.  

Halogeno- and Pseudohalogeno erivatives.—Silver difluoride can be used to fluorinate (23) selectively. 

The chlorocyclophosphazenes (NPCysor are found to be excellent reagents for the conversion of acyl halides into nitriles  

No solvent was used, and typically the reaction mixture was heated to 150— 200 °C Oower when R = Alkyl), when the phosphoryl halide distilled off, leaving the nitrile in 50— 90% yield. 

Earlier correlations, relating the magnitude of the spin-spin coupling constant /p-N-p to the properties of the phosphorus substituents in cyclotri-phosphazenes, have been extended to include a wider range of endo- and exo-cyclic substituents. When carbon replaces phosphorus in rings of the type (25), /p-N-p is reduced by a constant factor for a given substituent, and it was 

It was reported last year that C1 n.q.r. frequencies may be related to P—Cl bond lengths in chlorocyclophosphazenes. This point has been re-stated,  

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Activity in this area continues at about the same level as last year, although an increasing emphasis on the physical properties of the phosphazenes is apparent. On the chemical side, several novel routes to both acyclic and cyclic phosphazenes have been developed, and the aminocyclophosphazenes remain a major source of interest. 

Current progress in the synthesis and properties of pyrrolylphosphazenes is summarized. The differences in reactivity of the cyclic trimer (NPC12)3, and high polymer (NPC12)X, toward the pyrrolide nucleophile are discussed. Efforts to induce electronic conductivity in the polyphosphazenes are reviewed with particular emphasis on polybis (pyrrolyl) phosphazene. 

Physical and Spectral Properties of Perfluoro Cyclic Phosphazenes... 

Among inorganic heterocycles, perhalogenated cyclic phosphazenes occupy a very prominent place as the precursors for polyphosphazenes whose properties can he tuned by changing the substituents on the phosphorus sites (J). The heterocycles, as such, provide a robust framework for building a variety of novel molecules that have high thermal stability and flame retardancy, and have also been used recently to prepare a variety of dendrimers (2). The most widely studied among these are the perchlorinated cyclophosphazenes. Their syntheses reactions, properties, and application potential have been well documented a, 3-7). 

The polymeric phosphazenes are treated in chapter (see Polyphosphazenes) A recent monograph covers the chemistry of polyphosphazenes (nomenclature, synthesis of cyclic monomers , ring opening polymerization, condensation polymerization, substitution, polymer properties, and applications more than 1000 literature citations). Other reviews have also been published recently. Sulfur-containing polyphosphazenes have also been described. ... 

Species that combine the properties of organosilicon compounds and phos-phazenes are prepared by the linkage of organosilicon side groups to a small molecule cyclic or linear high polymeric phosphazene skeleton. This is particularly important for high polymeric derivatives in which hybrid properties typical of polysiloxanes (silicones) and polyphosphazenes - may be obtained. 

In the reduction with 2,2 -bipyridyl, redox reactions are absent and the limiting stage is the transfer of the 2nd electron, [AEo being —60 to —70 mV. Reduction of the nickel(II) complex with PPhs, ( PrO)3P, PhP(OBu)2, or (PhO)3P is limited by the transfer of the 1st electron and is accompanied by comproportionation (PPh3, AEo= 90 mV) and disproportionation reactions (phosphites, AEq< 0). The redox properties of some transition metal-cinnamonitrile cyclo-phosphazene derivatives, e.g., 107-109 have been stuoied by cyclic voltammetry (CV) and controlled potential electrolysis (CPE) in aprotic media. 

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