Fluorophosphoranes, reactions

Monomeric phosphazenes are, perhaps unexpectedly, obtained20 from the reactions of certain lithiated imides with fluorophosphoranes ... 

In the course of a study of the formation of fluorophosphoranes from chloro-phosphines (22) we observed one exception in the compound chloromethyldi-chlorophosphine, which reacted smoothly with antimony trifluoride to give the flammable fluorophosphine, C1CH2PF2, under conditions where many other chloro-phosphines were invariably converted into fluorophosphoranes. As this fluorophosphine is readily available, its interaction with a metal carbonyl derivative was studied, and cycloheptatriene molybdenum tricarbonyl, obtained from the reaction of molybdenum hexacarbonyl with cycloheptatriene (I, 2), was chosen as a starting compound. 

Note added in proof In May 1975 The and Cavell have reported (86b) the successful synthesis of dimethyltris(trifluoromethyl) and trimethylbis(trifluoromethyl) phospho-rane from the reaction of tetramethyllead with suitable fluorophosphorane precursors. The compounds are stable white solids of trigonal bipyramidal structure. 

Table 2. Fluorophosphoranes Obtained by the Reaction of Tributylphosphane with Fluorinated Alk-l-enes ...

New silylated imino-phosphor anes, e.g. Ph2P(=NSiMe3)(CH2) P-(=NSiMe3)Ph2 (where n = 1—3), are the products of reactions between azidotrimethylsilane and the corresponding bis-phosphine at 140°C 375 de-silylation can be achieved by fluorophosphoranes [see equation (13)] to give diphosphazaphosphonium salts (57). Monomeric phosphoramidimidic di-... 

The reaction of trialkyl phosphites with perfluoroalkenes in an autoclave at l(X)-140°C results in the formation of dialkyl perfluoroalkenylphosphonates in low to good yields (21-81%, Scheme 3.7). " The mechanism involves the attack of the phosphite nucleophile at the polarized terminal CF2 position to form a perfluoroalkenyltrialkoxyfluorophosphorane, which is stable under the usual conditions. This fluorophosphorane, which may be regarded as an isolable Michaelis-Arbuzov intermediate, decomposes on heating with elimination of alkyl fluoride to give dialkyl perfluoroalkenylphosphonates (Scheme 3.7). ... 

A report that C2H6PF2 and C2H5PFCI are formed in the antimony trifluoride-ethyldichlorophosphine reaction (134) was later shown to be erroneous (289), and the products correctly identified as ethyltetra-fluorophosphorane, C2H5PF4, and its hydrolysis product ethylphos-phonic difluoride, C2H6POF2. 

Indeed the reaction between alkyl- or arylchlorophosphines R PCls and either antimony (or arsenic) trifluoride in the absence of solvent offers a convenient route to the pentavalent fluorophosphoranes R PFg (151, 283, 286, 298). 

The exchange reactions between fluorophosphoranes and silane derivatives have been utilized for the fluorination of alcohols, via their trimethylsilyl ethers (89). > According to one of these reports, the alkyl fluoride is generally accompanied by olefin. Phosphorus penta-fluoride similarly fluorinates siloxanes such as (90). ... 

Salts are produced by the reaction of fluorophosphoranes with A -silylimines (94). Vinyl isocyanate reacts with phosphorus penta-chloride to give a hexachlorophosphate salt (95), which yields the phosphonic dichloride (96) on hydrolysis and distillation. Butyl cyanate reacts with phosphorus pentachloride to give two products, (97) and (98). ... 

The synthesis of the tetrazaspirophosphoranes (113, X=Br or I) was achieved by the reaction of (112) with trimethylsilyl halides whereas (113, X=CN) was obtained by metathesis of (112) with NaCN. The route to (113,X=F), however, involves the reaction of the fluorophosphorane (114) with the silyl urea (115). The compounds were characterised by mass spectrometry, i.r., multinuclear n.m.r. and X-ray crystallography. ... 

Oxidative fluorination of alkyl- or aryl-phosphines R PH3 for R = Ph, C6Hu, or NCCH2CH2 occurred on reaction with xenon difluoride, but with the chlorides Ph PCl3 there was also chlorine substitution, and the products were the normal phenyl fluorophosphoranes. In the presence of PhPp4, phosphorus trifluoride can be inserted into the C—F bond of 1-adamantyl fluoride to produce the previously inaccessible l-adamantyltetrafluorophosphorane ° substitution of PF3 by Bu Pp2 or 1-adamantyldifluorophosphine led to, respectively, 1-adamantyl-t-butyl-trifluorophosphorane and bis( 1 -adamantyl)trifluorophosphorane. 

Fluorophosphoranes can be obtained from phosphonous and phosphinous halides by reactions with arsenic or antimony obtained with KHF2 (6.518). Some phosphinous halides react with sulphur compounds to give phosphinothioites (9.420), with phenyl azide to give monophosphazenes (7.447), and with ylids fluorides (6.504, 6.505). Hydrofluorophosphoranes produces phosphonium salts (6.377). Phosphonous and phosphinous halides can be condensed to form polyphosphines or cyclic derivatives (6.660, 6.666,6.680,6.684), or reacted to give P-P linkages (6.737). 

Fluorophosphoranes and halophosphines usually break Si-N linkages and replace them with P-N, without forming either Si-P or Si-N-P linkages (7.135,7.179,7.256,7.458,7.488,7.489). In the absence of these reagents, however, the grouping P = N-Si is relatively stable (7.490) and (7.529). Some reactions of silyl iminophosphoranes are given in Chapter 7.10. 

Fluorophosphoranes were prepared from triphenylphosphine, di-zso-propyl azodicarboxylate and potassium hydrogen fluoride in acetonitrile (Eq. 28) 0 The first step is the addition of PPh3 to the azo bond (Mitsunobu reaction) followed by the reaction of the betaine with fluoride ions. Sonication facilitates the reaction of the insoluble alkali fluoride. However, it can be observed that recent works tend to demonstrate the occurrence of SET mechanisms in the Mitsunobu reaction. ... 

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