Crystal Structures of Phosphazenes

Studies on partially hydroxylated products of organocyclo-phosphazenes have clearly shown that such compounds exhibit tauto-merism involving 0 —> N hydrogen transfer. The crystal structures of N3P3Ph2(0Me)3(0)H (110), N3P3Cl2(NEt2)3(0)H (111), and... 

P—S bond is elongated to 196.5 pm and the P—0(H) bond shortened to 148 pm.164 The structures of the m-vinyl carbonate (136)165 and the cyclic phosphonic anhydride (96)123 have been determined, and for the latter compound the ring was found to be almost planar. A -Ray diffraction data of deoxyuridine phosphate,166 phospholipid multilayers,167 nucleotides,168 and skeletal muscle169 have been analysed. The crystal structure of the phosphazene (137) has been established.170... 

Deprotonation of [NP(NHC6H40Me-2)2]3 with twelve equivalents of Bu"Li in thf has been reported to yield the dodecanuclear lithium complex [Lii2 NP(NC6H40Me-2)2 3(CH2 = CH0)6(thf)6]. In the crystal structure of this complex six lithium atoms are located on each side of the phosphazene ring. ... 

There have been few important advances in this area during the past year. The first crystal structure of a phosph(m)azene, Bu (Me3Si)NP=NBu, has been reported, and the claim made last year, of the formation of a compound containing a phos-phazene linkage which forms part of a four-membered ring, has been shown to be erroneous. The formation and properties of cyclophosphazenes (mainly amino-derivatives) and the phosphazene polymers have been reviewed. The patent literature is the most important growth area, particularly where flameproofing applications are concerned. 

The crystal structures of glycylaminomethylphosphonic acid, and of methane-, ethane-, and propane-diphosphonic acids, have been determined. The unit cell of the last acid contains two molecules, with different conformations. The molecular structures of the constrained phosphite (161), the phosphate (162), and the thio-phosphate (163) have been compared. The nitrogen in the last compound is very nearly trigonal planar, and the large P—N distance (313 pm) shows that there is little P - - N interaction. The phosphazene (164) adopts a novel conformation, ... 

Hydrolysis of chlorocyclophosphazenes affords hydroxy oxophosphazanes via a rapid tautomerism of the initially formed dihydroxy phosphazenes (Eq. 28) [147-149]. Crystal structure investigations on N3P3(0Ph)s(0)(H) [150],... 

It is exceedingly difficult to determine the molecular structure of a synthetic macromolecule. X-ray diffraction—the ultimate structural tool for small-molecule studies—yields only limited information for most synthetic high polymers, and crucial data about bond lengths and bond angles are difficult to obtain.47 However, that same information can be obtained relatively easily from single crystal X-ray diffraction studies of cyclic trimers, tetramers, and short-chain linear phosphazene oligomers. The information obtained may then be used to help solve the structures of the high polymeric counterparts. 

The bicyclic phosphazene III forms colorless crystals that are stable in air and melt sharply at 124°. The compound is readily soluble in petroleum, benzene, chloroform, and dichloromethane but insoluble in water. The IR spectrum of the compound shows a broad absorption band at 1195 cm" attributable to ring P=N stretching vibration. The H NMR spectrum is discussed in the literature,The P H NMR spectrum is that of an A2BC spin system (8 18-24). The structure of the compound has been established by X-ray crystallography. The crystals are monoclinic with space group C2/c, a = 10.81, b = 17.52, c = 28.48 A, p = 94.8° with eight molecules in the unit cell. 

An ab initio study of structure and bonding in diphosphinylcarbenes indicates that the non-symmetric ylide-type structure (29) is preferred." The configuration and conformation of a number of polyfunctional 1-aminobuta-1,3-dienes (30), prepared by the reaction of dimethyl acetylenedicarboxylate with (Z)-P-enamino-l -phosphazenes, have been studied by n.m.r.. X-ray, and theoretical methods. The P n.m.r. spectra of a number of protonated iminophosphorane-substituted proton sponges, e g. (31), of known crystal structure have been studied in the solid state."... 

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