Phosphine Radicals

Phenyl derivatives of phosphole and phosphorin will react with alkali metals at low temperatures to produce radical anions which can be represented as Equation 13.206. As the temperature is raised, phenyl radicals are obtained. 

Triphenylphosphine reacts with alkali metals in tetrahydrofuran to give initially metal phosphides which on further reaction at low temperature produce radical anions (13.207) and (6.921). Triphenylphosphine oxide reacts with potassium in THE to give potassium phosphyl— an analogue 

---

Phosphole radicals are known to be more readily made and more stable than analogous phosphine radicals . This is probably due to the delocalization of the unpaired electron over the ring. On the other hand, complexes such as XLVIII are isolated from the reaction mixture and their mass spectra contain a medium-intensity peak corresponding to the final phosphaferrocene however, their thermolysis in the pure state does not produce phosphaferrocenes in detectable amounts. Phenyl-substituted phosphaferrocenes are always among the by-products of the synthesis of phosphaferrocenes. No satisfactory explanation of this fact (the formation of phenyl substituted phosphaferrocene by radical arylation as initially proposed is not very likely since ferrocene cannot be arylated in this way could be found until the very recent discovery that, at around... 

Phosphite (phosphonate) and hypophosphite (phosphinate) radicals are produced from phosphites and hypophosphites by y-ray excitation of their crystalline salts, or by oxidation of their alkaline solutions. 

Character of influence phosphinate trivalent iron on mechanical properties the block-copolyesters practically reflects influence of other salts of bivalent metals the tendency to reduction of explosive durability of compositions on a basis phenolphthalein a block-copolymer is evidently shown at increase of number phosphinate radicals in phosphor organically salts, that in turn depends on valency of metal. As to compositions on a basis bisphenol A the block-copolyester and iron (III) phosphinate here mechanical parameters remain on enough high level. 

Muneer, R. and Nalli, T.W., Use of diaryhodonium/phosphine radical-chain chemistry for visible photoinitiation of cationic polymerizations, trimethyl phosphite as a co-initiator of the ringopening polymerization of cyclohexene oxide. Macromolecules, 31, 7976, 1998. 

Commercial phosphine derivatives are produced either by the acid-cataly2ed addition of phosphine to an aldehyde or by free-radical addition to olefins, particulady a-olefins. The reactions usually take place in an autoclave under moderate pressures (<4 MPa (580 psi)) and at temperatures between 60 and 100°C. 

There are a few economical routes that can be employed for production of the largest-volume phosphines as specialty chemicals. The preparation of alkyl phosphines, where R > C2H, employs the addition of lower phosphines across an olefinic double bond. The reaction may be either acid-, base-, or radical-catalyzed. The acid-catalyzed addition probably proceeds through the generation of a carbonium ion intermediate which is attacked by the unshared... 

The addition of phosphines to fiuoroolefins is of free radical nature [6, 7, (equations 2-5)... 

The decomposition of di- e -butyl peroxide in the presence of diethyl phosphite and an aromatic substrate leads to free-radical phosphination, Eqs. (43) and (44). 

The evidence is that the thermolytic route does not involve radicals but the photochemical one does. A dissociative mechanism for the thermolytic route is indicated by its inhibition by added phosphine it is likely that once a phosphine group has dissociated, a metal-hydrogen bond is formed, with generation of a coordinated alkene (Figure 3.58). 

The acyl phosphonates, acyl phosphine oxides and related compounds (e.g. 81. 82) absorb strongly in the near UV (350-400 nm) and generally decompose by rescission in a manner analogous to the benzoin derivatives.381"285 Quantum yields vary from 0.3 to 1.0 depending on structure. The phosphinyl radicals are highly reactive towards unsaturated substrates and appear to have a high specificity for addition v.v abstraction (see 3.4.3.2). 

Phosphinyl radicals (e.g. 103-107) arc generated by photodecomposition of acyl phosphinates or acyl phosphine oxides (see 3.3.4.LI)282,466 474,473 or by hydrogen abstraction from the appropriate phosphine oxide.467... 

The nucleophilic displacement reactions with azide, primary amines, thiols and carboxylatc salts arc reported to be highly efficient giving high (>95%) yields of the displacement product (Table 9.25). The latter two reactions are carried out in the presence of a base (DBU, DABCO). Radical-induced reduction with tin hydrides is quantitative. The displacement reaction with phenolates,61j phosphines,6M and potassium phthalimide608 gives elimination of HBr as a side reaction. 

The reaction given here has been described before as a general reaction,2 and there can be a wide variety of alkyl, aryl, and halo substituents on the diene and phosphorus. Dibromophosphines are appreciably more reactive than dichlorophosphincs. If a free-radical catalyst is used instead of an inhibitor, the copolymers can be made in good yield.3 The 1,4-addition of dichloro-phosphines to 1,3-dienes is of theoretical interest because of its analogy to the well-known 1,4-addition of sulfur dioxide to 1,3-dienes. 

Examples of the intermolecular C-P bond formation by means of radical phosphonation and phosphination have been achieved by reaction of aryl halides with trialkyl phosphites and chlorodiphenylphosphine, respectively, in the presence of (TMSlsSiH under standard radical conditions. The phosphonation reaction (Reaction 71) worked well either under UV irradiation at room temperature or in refluxing toluene. The radical phosphina-tion (Reaction 72) required pyridine in boiling benzene for 20 h. Phosphinated products were handled as phosphine sulfides. Scheme 15 shows the reaction mechanism for the phosphination procedure that involves in situ formation of tetraphenylbiphosphine. This approach has also been extended to the phosphination of alkyl halides and sequential radical cyclization/phosphination reaction. ... 

---