Fluorophosphoranes

Our own geometry optimizations confirmed the preference for equatorial methyl groups, but we could discern no significant difference in the spin-coupled description of axial and equatorial P—CH3 bonds. This seems to suggest, at least for these systems, that the geometric preference is more closely linked to steric factors than to details of the bonding. 

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

Penta-coordinated fluorophosphoranes have been extensively considered by Schmutzlera965,12andl4) and discussed in detail in ref. 1966, 1, p. 281 seq. The special interest was in the existence of two well-defined types of fluorine substituents, as well as for the hexa-coordinated (PVI)e compounds. Fluorine exchange generally occurs by pseudorotationf but steric hindrance, substituent conjugation and low temperatures may stabilize fluorine atoms in their respective position. As a rule (see Section... 

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. 

Iodine pentafluoride can be employed for mild selective oxidative fluorination. Aryl- and al-kylphosphanes R3P, R2PF, R2PC1, and RPC12 are oxidized by iodine pentafluoride to the corresponding fluorophosphoranes at or below 0 C.138 In dichloromethane, the fluorination proceeds more readily than in acetonitrile which is prone to coordination. The yields of the products are 50-70%. 

This initial hypothesis was subsequently refined by the deduction of two preference rules for the structures of the intermediate pentacovalent phosphorus derivatives, the phosphoranes. Muetterties and Schunn65. in order to rationalize the nmr spectra of a number of alkyl fluorophosphoranes (CH3) -PF5 . formulated the hypothesis that the more electronegative fluorine atoms... 

As in the above case for the alkyl fluorophosphoranes. the H1 nmr spectrum of the oxyphosphoranes possesses features which are only readily interpretable in terms of a pseudorotation mechanism68-66. The H1 spectrum of the cyclic tetraoxyalkylphosphorane synthesized from trimethylphosphate and 3-benzylidene-2,4-pentadione shows two kinds of methoxyl groups at low temperature (—65°C), a single methoxyl signal at room temperature, and a... 

The high stability of fluorophosphoranes gives rise to addition products of the phosphorane series. Some examples are recorded in Scheme 21 (72CC272, 74MI11701, 64SA1835, 65MI11701, 70RCR1). 

In 1974 a DuPont patent- disclosed the synthesis of cyclen phosphine oxide, 2,— by hydrolysis of cyclen fluorophosphorane, 1. 

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. 

R. Schmutzler, Fluorophosphoranes, in V. Gutmann, Halogen Chemistry 2, 31, Academic Press, New York 1967. 

Irregular permutational isomerizations of certain fluorophosphoranes, (55) and (115), were recently reported.132... 

Figure 5 Spin-coupled orbitals for a typical P—CH3 bond in fluorophosphoranes.

Both observed the monoaddition products 30, but the phosphanediols 31 have been found only by Roschenthaler (227). While the methylated compound 31b decomposes above 45°C, the phosphane derivative 31a has been found to be air-stable. Dimethylphosphane was claimed by Bruker and co-workers (43) to yield the alcohol 32a, which could not be confirmed (227). Instead, the oxidation product 33a has been found together with a diphosphane 34 and fluorophosphorane 35 (227). 

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

Fluorophosphoranes are derivatives of phosphorus (V) fluoride of the composition R PF6 , where n = 1 to 3 and R may be an aliphatic or aromatic hydrocarbon group. Unlike the formally analogous and long-known chloro compounds, R PCl6 , fluorophosphoranes are typical covalent... 

Tetrakis(l,l,l-trifluoro-2,4-pentanedionato)zirconium and (hafnium), S3mthesis 14 Fluorophosphoranes, synthesis 18 Phenyldibromophosphine, synthesis 19 Phosphonitrile fluorides, synthesis 20... 

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