Phosphonitrile compounds

Allcock HR, Kugel RL, and Valan KJ. Phosphonitrilic compounds. Vll. High molecular weight poly (diaminophosphazenes). Inorg Chem, 1966, 5, 1716-1718. 

Phosphazenes, formerly known as phosphonitrilic compounds, are characterized by the presence of the group P=N. Known compounds, particularly those containing the —p=n— group, are very numerous and they have important potential applications. 

A large number of derivatives of the phosphonitrilic compounds can be prepared by means of the reactions at the P-Cl bonds. Hydrolysis reactions produce P-OH bonds that can then undergo esterification reactions. Substitution reactions that replace two chlorine atoms can occur at the same phosphoms atom (giving a geminal product) or on different phosphorus atoms. In the latter case, the two substituents can be on the same side of the ring in cis positions or on opposite sides of the ring in trans positions ... 

Although a comprehensive chemistry of phosphonitrilic compounds has been developed, the brief introduction presented here is adequate to indicate the types of compounds and the reactions they undergo. 

The patent literature on the phosphonitrilic chlorides is extensive no attempt will be made to deal with it here. Most proposed applications have been to the high-polymer field, particularly where resistance to high temperatures is required. Phosphonitrilic compounds have proved valuable in flame-proofing treatments for fabrics and have been suggested as plasticizers, as oil additives, and as catalysts in silicone manufacture. 

The reactions of phosphonitrilic compounds may be conveniently considered in four groups polymerization, reactions with donor molecules, alkyl and aryl derivatives, and reactions with acceptor molecules. The relation between structure and reactions will be considered in Section V. 

Other donor molecules react with phosphonitrilic compounds. Dioxane is said to facilitate the depolymerization of the high polymer (63) and of the phenyl derivatives (13). Acetone forms complexes with the amino acid derivatives of the tetramer (see p. 128 in ref. 3). It is possible that ether acts as a catalyst for the hydrolysis of the trimeric chloride. The effect of these solvents is subtle, since the solubilities of the trimeric chloride in ether, in pyridine, and in dioxane show no sign of any specific chemical interaction. 

In many of the reactions referred to above, the phosphonitrilic compounds have behaved as acceptors hydrolysis, esterification, aminolysis, and fiuorination can all be understood in terms of nucleophilic attack at the phosphorus atom. Phosphonitrilic compounds also possess marked donor properties, though these have not been studied systematically until recently. 

The foregoing chemical reactions have shown the retention of the ring structure of the phosphonitrilic compounds through a variety of reactions in which the chlorine atoms are replaced by other electronegative substituents. They have chiefly concerned the trimeric and tetra-meric chlorides, because these are more abundant than the higher polymers. It is known, however, that the pentameric chloride, for instance, is both thermally stable and resistant to hydrolysis. The higher polymers have not yet been separated but the mixture of approximate composition (PNCl2)8-9 is also comparatively inert. The individual members of... 

The original aim, which remains unchanged, was a text-book of modest size and price that did not presume to be a substitute for oral instruction or seek to deal with the special topics which give individuality to advanced courses. Extending its scope to include even a selection of these topics would have destroyed the character of the book hence the only major additions are a description of phosphonitrilic compounds, a section on complexes in aqueous solution, and a short chapter on inorganic polymers. In other parts the treatment has been modified to bring it into line with the results of recent research. 

What comprises a polymer A general definition, which can include natural, modified natural (semisynthetic), and purely synthetic polymers of all types is that a polymer is a large molecule built up of small structural units combined in any conceivable pattern. Staudinger, a major contributor to the early development of polymer theory, set as an arbitrary guideline that a polymer was a molecule with a molecular weight of more than 10,000, or that consisted of a total of more than 1,000 carbon atoms. While there are also a number of important polymers with an inorganic backbone, such as silica, the silicones, and phosphonitrilic compounds, where the second criterion would not apply, they would still qualify under the first. 

Other compounds These include many sulfides, phosphonitrilic compounds with ring and chain structures, and compounds with metals, which are generally of low ionic character. 

Phosphazenes or Phosphonitrilic Compounds Phosphazenes are a group of compounds represented by the general formula (NPX2)/7 where X = F, Cl, Br, SCN, CH3, C6H5 etc. All these compounds are... 

A great many compounds are known with P—N and P=N bonds.47 R2N—P bonds are particularly stable and occur widely in combination with bonds to other univalent groups, such as P—R, P—Ar and P—halogen. The entire subject of P—N compounds cannot be properly outlined in the space available. Hence, only one part of it, the chemistry of phosphazenes (also called phosphonitrilic compounds), will be described in detail. 

Certain phosphonitrilic compounds fall into the class of pentavalent phosphorus halides (186). Hexachlorocyclotriphosphazene (23) is... 

H.R. Allcock, W.J. Cook, D.P. Mack, Phosphonitrilic compounds. XV. High molecular weight poly[bis(amino)phosphazenes] and mixed-substituent poly(aminophosphazenes), Inorg. Chem. 11 (11) (1972) 2584-2590. 

The last product is apparently the diazodiarsacyclobutane (n = 2). Another cyclic arsenical has been prepared (299) using a method developed for preparing the corresponding phosphonitrilic compounds. 

Phosphazenes (formerly known as phosphonitrilic compounds) may also be called azaphosphenes (Section 7.1). They are characterised by the presence of the group P=N. Known compounds, particularly those of the XV variety, are very numerous. Phosphazene chemistry has received a great deal of attention over the past 40 years. Although products with very diverse and important applications have been evolved, extensive commercialisation of these has not yet taken place. 

Phosphorus(V) chloride gives with liquid ammonia a series of phosphonitrilic compounds ... 

Allcock, H.R. and Kugel, R.L. (1966) Phosphonitrilic compounds V Cyclized products from the reactions of hexachlorocyclotriphosphazene (phosphonitrilic chloride trimer) with aromatic dihydroxy, dithiol... 

Semiempirical valence electron molecular orbital methods were used to evaluate the electronic structure of derivatized phosphonitrilic compounds. All molecular structures were fully force optimized with no geometric constraints other than obvious symmetries. Structural parameters for initial geometries were taken from available x-ray crystal structure determinations whenever possible. Although pre-... 

Ferris, K. F., and Risser, S. M., Bond alternation in phosphonitrilic compounds, Chem. Phys. Lett., 174, 333 (1990). 

Consider the hypothetical cyclic phosphonitrilic compound [N4(PX2)2]. After taking care of the cr bonding, it is assumed that the participating atomic orbitals for the n bonds around the ring are the four nitrogen orbitals and two phosphorus orbitals. These orbitals are shown and labeled below, where only the signed lobes above the molecular plane are displayed. 

AUcock, H. R., Kugel, R. L., Valan, K. J., Phosphonitrilic compounds. VI. High molecular weight poly(alkoxy- and aryloxyphosphazenes). Inorganic Chemistry, 1966, 5, 1709-1715. 

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