Cyclophosphazenes

The number of reviews about cyclophosphazenes is limited. Cyclocarbaphos-phazenes have been reviewed/as well as applications of cyclophosphazenes. Calculations show that 1,2-azaphosphinines and 1,3,2-diazaphophinines possess a higher reactivity as compared to their 1,3-aza and 1,3,5-diaza isomers as a consequence of larger electrophilic character of the phosphorus atom.  

In contrast to the amino-substituted cyclophosphazenes, many papers have appeared concerning alkoxy and aryloxy substituted phosphazenes. A one-pot procedure based on phase-transfer catalysis has been developed for the preparation of N3P3 0C6H4[C(0)H-4] 6 and N3P3 0C6H4[C(0)Me-4] 6.  

N3P3[OC6H4(N=NAr-4)]e have been synthesized and fully characterized by spectroscopic methods.  

Crystals of tris(o-phenylenedioxyde)cyclotriphosphazene (97) can act as hosts for the inclusion of a number of organic polymers, e.g. cis-1,4-poly butadiene, 1,4-polyisoprene, polyethylene (PE), poly(ethylene oxide) (PEO) and polytetrahydrofuran. X-ray studies of the PE and PEO inclusion compounds show that the polymer chains are extended along the tunnel-like voids of the host lattice. The formation of clathrates appears to be limited by the tunnel dimension of the host crystal lattice. The melting points of the inclusion adducts appear to be higher than those of either the pure host or the pure 

Studies of the reactivity of l,3-a 5a-oxy(tetraethyleneoxy) derivative (99) have been extended to reactions with alkylene diamines. Substitution takes place at the PCI centre as a consequence of the interaction between the incoming nucleophile and the crown ether ligand already present, yielding compounds (100), (101) and (102). Only for H2N(CH2)3NH2 was the formation of a spiro derivative (103) was observed. Treatment of (99) with an excess of nucleophilic reagents leads to substitution of all chlorine 

Reviews of cyclophosphazene chemistry have focused on several important subtopics rather than comprehensive surveys or overviews. A comprehensive review of polymers derived from addition polymers of olefins attached to cyclophosphazenes has appeared. Synthesis, copolymerization and quantitative studies of monomer reactivity are discussed in detail. A comprehensive two part review of hybrid phosphazene-siloxane systems includes cyclophosphazenes with siloxane substituents and polymers derived from hydrosilation of alkenylphosophazenes. A survey of new generation candidates for currrently banned Halon fire extinguishing agents concludes that phosphazenes are superior to halons in lab scale extinguishment tests.  

The reactions of halophosphazenes with nucleophiles continues to be utilized as one of the major routes to new cyclophosphazene derivatives. Fluorophos-phazenate anions are obtained by the reactions of fluorocyclophosphazenes with (Me2N)3S Me3SiF2l, an effective fluoride ion donor. The trimer yields 10 as the 

3-napthalenediol and 2,2 -biphenol and the dispiro derivative of the biphenol. Replacement of the remaining fluorine atoms of the mono spiro derivatives can be accomplished using the o-, m- or p- FC6H40SiMe3 reagents.  

Mixed Main Group-Phosphazene Ring Systems Including Cyclophospha(thia)zenes 

Polyphosphazenes have an intimate relationship with their cyclic counterparts. It is essential to obtain an understanding of the structure and reactivity of the cyclic derivatives in order to be able to extend this chemistry to the polymeric analogues. In this chapter, we will therefore, first discuss cyclophosphazenes and then move on to polyphosphazenes. Other polymers related to the polyphosphazene family will be discussed in subsequent chapters. 

Most cyclophosphazenes are relatively stable and have good shelf lives. Some are sensitive to moisture. Even, the chlorocyclophosphazenes, N3P3CI6 and N4P4CI8 can be readily handled in open air (in a well-ventilated hood). Most persubstituted cyclophosphazenes have very low dipole moments and this is reflected in their excellent solubility properties even in nonpolar organic solvents. Table 3.1 summarizes the melt-ing/boiling point data for some of the prominent members of the cyclo-phosphazene family. 

Focused reviews of various aspects of cyclophosphazene chemistry including the relation of exocyclic substituents to polymerizability and synthetic transformations of organometallic and bioactive phosphazenes , a summary of variables involved in the synthesis of bicyclic phosphazenes 

A brief comparison of phosphorus-nitrogen bond lengths relative to phosphorus-oxygen systems leads to the suggestion 

The reactions of (NPCl2)3 4 and N P (NHEt) 2C1 with excess pyrrolidine lead to the known pyrrolidine derivatives and the amidinum salt CH3 (C HgN)C=NH HC1 the formation of which was 

N3P3Cl5NH(CH2)gNHN3P3Cl5, at a slower rate with parameters 

X=Y=NMe, n=2,3 X=NH, Y=NMe, n=2,3 X=0, Y=NMe, n=2) has been prepared for NMR studies (yida ante). The cytotoxic effects of some new aziridinylcyclophosphazenes have been reported. Inorganic syntheses preparations of NjPjAz Cl. (Az = aziridine  

The unsaturated four-membered P2N2 ring is also stabilised by the formation of diadducts with Lewis acids, which are surprisingly formed in the reaction of Ph2PCl with bis(trimethylsilyl)sulfur diimide with Gads or AICI3 [eqn 

In an interesting adaptation of the cyclocondensation synthesis depicted in eqn (11.26), both the cis and irons isomers of non-geminally substituted [(Ph)(Me)PN]3 have been prepared and separated by using column chromatography on silica gel [eqn (11.27)]. °  

The remarkable, highly charged hexacation [P3N3] , which is formed in the reaction of (NPCl2)3 with 4-(dimethylamino)pyridine (HMAP) in superheated 

The Lewis basicity of cyclophosphazenes is enhanced by replacement of the chlorine substituents by electron-donating groups, e.g. Me or Me2N, as illustrated by the formation of complexes of (NPMe2) ( = 6, 8) with transition metal 

The binary anion [PsNg], which is found in the solid state in the ternary compound LiPNs, has a chair-shaped P3N3 ring (11.20), cf. the isoelectronic cyclotrisilicate [SisOg] (see 10.43 in Section 10.5). 

These polypodants have been described as powerful complexing agents towards alkali metal ions and hence strong anion activators. Some tris(aryl-dioxy) derivatives of (NPCl2)3 have been reviewed including their ability to form clathrates with aromatic organic molecules such as benzene, styrene, etc. Selectivity for inclusion of aromatic molecules has been discussed in relation to the structure of the host molecules.  

X-Ray structure determinations show that, in compounds 21, 22, and 23, the metal is coordinated to two non-geminal exocyclic nitrogens and one endocyclic nitrogen (ti ). In compound 20 two coordination modes are present, viz. and NMR studies reveal for these compounds a complex fluxional behavior.  

Syntheses of alkoxy and aryloxy substituted cyclophosphazenes still forms an important research item, in particular as the knowledge thus obtained can be used for the preparation of the corresponding polymers. 

Synthesis of mono and disubstituted products (NPCl2)2NPCl(OC6H2Bu 3- 

6) 2]2NP(OC6H3Bu 2-2,6) 2 have been reported for reactions of (NPCl2)3 with corresponding sodium aryloxides. The formation of bicyclic compounds has been explained by a metal-halogen exchange mechanism.  

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Sulfanuric halides contain the characteristic group -N=S(0)X- (X = Cl, F). Unlike the isoelectronic cyclophosphazenes (NPClajx (x = 3-17), " only six-membered rings have been well characterized. The sulfanuric halides are colourless solids (X = Cl) or liquids (X = F), which are stable in dry air. Sulfanuric chloride [NS(0)C1]3 is best prepared by treatment of SOCI2 with sodium azide in acetonitrile at -35°C (Eq. 8.16). It may also be obtained as a mixture of a- and yS-isomers in a two-stage reaction from H2NSO3H and PCls. The fluoride [NS(0)F]3 is formed as a mixture of isomers by the fluorination of [NS(0)C1]3 with Sbp3. ... 

Mechanism of phase-transfer phenolysis of chlorinated cyclophosphazenes 99MI20. 

Cyclopentene-l-dithiocarboxylic acid, 2-amino-meta complexes, 2, 800 Cyclophane chlorophylls, 3, 58 Cyclophane hemes iron complexes, 4,1269 Cyclophosphazenes metal complexes, 2, 81 Cyclopropane carbonylation... 

The diazaphosphane or aminoiminophosphane ligands with a NPN framework are another subclass of cyclophosphazenes. These compounds with both phosphorus in oxidation state (111) [104-110] and (V) [111-112] have been employed in the synthesis of four membered heterocycles and coordination chemistry with group 13 derivatives. Several complexes of trivalent phosphorus derivatives with both aluminum halide and alkyls are known as illustrated for 48 in Scheme 21 [113-119]. The structure determination of 48 confirms the formation of a four membered metallacycle [116, 117],... 

Process III Preparation of Polyphosphazenes by Ring Opening Polymerization Processes of Substituted or Partially Substituted Cyclophosphazenes... 

The problem of the thermally induced polymerization reaction of partially or completely substituted cyclophosphazenes has been considered in the past by several authors [355-357], and more recently by H. R. AUcock [358]. This is because of the ease of synthesizing these substrates, the possibihty of preparing structurally regulated poly(organophosphazenes), and the lack of any additional nucleophilic substitution processes on the poly(organophosphazenes) obtained by the ROP process of fully saturated trimers. 

When the ROP process is attempted on partially or completely substituted cyclophosphazenes in molten state several phenomena can take place ... 

The occurrence of one of these situations rather than another depends on the chemical nature of the cyclophosphazene exploited and on the experimental conditions selected for the polymerization process. These facts are illustrated in Table 3. 

Table 3 Influence of experimental parameters on the reactivity of partially or completely substituted cyclophosphazenes during a ROP process...

An important comprehensive review of the cyclophosphazenes (including dimeric monophosphazenes) has appeared. 

Derivatives of the type, RjP N=P(NH2)X 2, were obtained by displacement of the chlorine atoms marked with an asterisk by ammonia. The parent halides decomposed at ca. 150 °C giving, amongst other products, cyclophosphazenes, (NPR2) , and phosphazene polymers. 

Examples of cyclophosphazenes with ring systems containing elements other than phosphorus or nitrogen continue to be reported. The linear phosphazene [Ph2(H2N)Pi N.i P(NH2)Ph2]+Cl is cyclized by antimony pentachloride to give the compound (35). This result contrasts with... 

An interesting series of ammonolysis and aminolysis products has been obtained from the cyclophosphazene (36) (see Scheme 2). It is note-... 

The reactions of alkylaminofluorocyclophosphazenes with hydrogen halides have provided a route to cyclophosphazenes with mixed halogen substituents ... 

The use of n-butylamino-derivatives of cyclophosphazenes in flame-proofing cellulose-based fabrics has been described in a patent application. The topic of fiame retardants is also covered in a recent review, where phosphazenes are important because of their relatively high phosphorus and nitrogen contents. 

B. Alkoxy- and Aryloxy-derivatives.—The preparation and physical properties of a series of thermally stable monoalkoxy (or aryloxy) fiuoro-cyclophosphazenes have been reported ... 

Mention has already been made of the application of alkoxycyclophos-phazenes, [NP(OR)2] , as flame retardants in rayon. Although the methoxy-derivatives, with their high phosphorus content, were expected to be most efficient in this respect, their water solubility proved a major shortcoming. However, the n-propoxy series, [NP(OPr )2] ( mainly 3—6), were found to impart excellent flame resistance and were well retained by rayon. The cyclophosphazene alkoxides were obtained by the addition of sodium-n-propoxide to the chloride homologues, (NPCl2)n, and were added to the viscose dope before the rayon was spun. The flame resistance imparted by various amino- and thioalkoxy-derivatives was also tested, but found to be inferior to the results obtained with alkoxy-deriva-tives. Several patent applications have resulted from work on this topic. ... 

The first example of an optically active cyclophosphazene (54) has been obtained by elegant experimental work. The route chosen is summarized in Scheme 5. 

Labarre, J.-F. Natural Polyamines-Linked Cyclophosphazenes. Attempts at the Production of More Selective Antitumorals, 129, 173-260 (1985). 

V. Cyclophosphazene-Based Ligands and their Coordination Chemistry... 

Cyclophosphazenes are a fascinating group of inorganic heterocyclic compounds whose chemistry is multi-faceted, well developed and reasonably well understood. They are closely related to the linear poly-phosphazenes this relationship is unlike any other existing between ring-polymer systems. Although cyclic siloxanes and polysiloxanes have a close interrelationship, the number and types of cyclophospha-zene derivatives that are known, together with their exact counterparts in polyphosphazenes, underscore the utility of cyclophosphazenes as models for the more complex polyphosphazenes. The literature on cyclophosphazenes has appeared earlier in the form of books (1,2), chapters of books (3-5), authoritative compilations of data (6,7), and several reviews (8-21). The current literature on this subject is reported annually in the Specialist Periodic Reports published by the Royal Society of chemistry (22). This review deals mostly with chlorocyclo-... 

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