Alkyl cyclophosphazenes

Fig. 15. (A) Cyclization reaction to afford a metallocyclophosphazene (20) (B) thermolysis of N-silyl-P-(fluoro)phosphoranimine (21) to afford alkyl cyclophosphazenes.

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],... 

Cyclization of linear fragments is one of the successful synthetic methods of preparing alkyl- or aryl-substituted cyclophosphazenes. An excellent synthon of this type is the Bezman s salt... 

Proton NMR has been extremely valuable in the structural elucidation of cyclophosphazene derivatives containing alkylamino, alkoxy or simple alkyl substituents [287]. 

Both colourless and deeply coloured compounds are found among the common unsaturated heterocyclic inorganic systems. For example, borazine B3N3H6 (see Section 4.1.2.1), like benzene, is a colourless liquid which exhibits a strong absorption band in the UV region. Similarly, cyclophosphazenes (NPX2) ( = 3-6 X = halogen, alkyl, aryl, alkoxy, dialkylamino) are also... 

There are numerous examples of the use of cyclophosphazenes with exocyclic dialkylamino or alkyl/aryloxy substituents on phosphorus as scaffolds for the formation of metal complexes. However, the number of complexes in which the endocyclic nitrogen atoms are involved in adduct formation with electrophilic... 

These compounds contain the characteristic group -N=S(0)X- (where X = Cl, F, alkyl, aryl, or R2N). Unlike the isoelectronic cyclophosphazenes, only six-membered rings have been well characterized. The sulfanuric halides are colorless solids (X = Cl) or liquids (X = F), which are stable in dry air. Sulfanuric chloride is best prepared by treatment of SOCI2 with sodium azide (equation 26). It may also be obtained as a mixture of a- and /3-isomers in a two-stage reaction from H2NSO3H and PCI5. The fluoride, [NS(0)F]3, is formed as a mixture of isomers by the fluorination of [NS(0)C1]3 with SbF3. 

Alkyl and Aryl Derivatives.—No new routes to alkyl-substituted cyclophosphazenes have been described, although trimeric and tetrameric homologues can be inter-converted on heating... 

The applications potential of cyclophosphazenes is apparent from the large number of patents and applications oriented studies which have appeared this year. The use of phosphazenes as flame retardants continues to represent the area of greatest activity. A comprehensive structure-activity study of the oxygen index, and thermogravimetric characteristics of several cyclo- and cyclolinear phosphazenes shows that flame retarding efficiency is in the following order NPCl2>NP(ORp) Cl>NP(0Rp)2>NP(0Rp) (OR) >NP(OPh) Cl>NP(OR) 2 (Rp=CH2(CF2) H, n=2,4,6 R=alkyl) Similar studies on... 

Unlike the isoelectronic cyclophosphazenes only six-membered rings have been well characterized for oligomers of the —NS(0)E— (E = F, Cl, alkyl, aryl or R2N) monomer unit. The trimeric chloride is best prepared by treating of SOClj with sodium azide in... 

There are other methods for preparing cyclophosphazenes containing P-C compounds. Condensation reactions involving the elimination MesSiX (X = Br, F) from N-(silyl)-P-(halogeno)phosphoranimines is a good method for the preparation of fully substituted alkyl- or arylcyclophosphazenes (see Eq. 3.19) [2, 14]. 

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