By Oxidation of Phosphines

By Oxidation of Phosphines.—The kinetics of the AIBN-catalysed autoxidation of various tervalent phosphorus compounds have been 

Razumov, E. A. Krasil nikova, N. A. Moskva, T. V. Zykova, and L. A. Chemo-danova, Zhur. obshchei Khim., 1971, 41, 2402. 

Miller, in Organophosphorus Chemistry , ed. S. Trippett (Specialist Periodical Reports), The Chemical Society, 1971, vol. 2, p. 56. 

A number of phosphine oxides and sulphides have been prepared by the oxidation of the corresponding phosphine using standard reagents, e.g. (21),2 , (22),a (23), and (4a) and (4b).  

Lindner and H.-D. Ebert, Angew. Chem. Internat. Edn., 1971, 10, 565. L. Maier, Helo. Chim. Acta, 1971, 54, 1651. 

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By oxidation of phosphine with an aqueous iodine solution ... 

The calcium salt is soluble in water, unlike that of phosphite or phosphate the free acid can be made from it or obtained by oxidation of phosphine with iodine in water. Both the add and its salts are powerful reducing agents, being oxidized to orthophosphate. The pure white crystalline solid is a monobasic acid (pK = 1.2). The more correct name of this acid, phosphinic acid, is rarely used, but when the... 

The phosphinium radical cation is the parent ion in the mass spectra of phosphines, phosphinites, phosphonites and phosphites. The triphenylphosphinium radical cation, PhjP+j is produced by y-ray irradiation of PhjP in dichloromethane or in sulphuric acid at 77 K. It has also been observed by oxidation of phosphines at a mercury anode, after which it combines with mercury as in Equation 13.209. Recent studies include radical cations of type PhEPHJ (E = N, P, As) [36]. 

Recently it has been found that the Heck reaction can proceed very well in water. In fact, the role of water in the Heck reaction, as well as other reactions catalysed by Pd(0) in presence of phosphine ligands is (i) transformation of catalyst precursor into Pd(0) species and (ii) the generation of zero-valent palladium species capable of oxidative addition by oxidation of phosphine ligands by the Pd(II) catalyst precursor can be affected by water content of the reaction mixture. 

The ability of phosphines to act as either one-electron acceptors or one-electron donors may be crucial in the mechanism of their cytotoxicity and allow them to interfere with electron transport processes. Phosphinium radical cations have been generated by oxidation of phosphines at a mercury anode or by y-irradiation of tertiary phosphines on silica and in sulphuric acid The oxidation potentials appear to be within the range accessible to biological systems Aryl phosphines are more easily oxidised than alkyl phosphines Ejq (polarography in CH3CN, anodic oxidation) PPha -H 50 mV, PEt3 - 415 Phosphine dimer cation radicals (R3PPR3) have been identified by... 

The standard heat of formation for crystalline H3PO2 is —608.8 kJ/mol (—145.5 kcal/mol) (39). The acid can be prepared by the oxidation of phosphine by iodine and water. 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

The osmium(IV) complexes are only obtained by this route with fairly unreactive phosphines and arsines (e.g. PBu2Ph) but they are conveniently made by oxidation of mer-OsX3(QR3)3 (Q = P, As) with the halogen in CHC13, or CCI4 and refluxing. 

Oxidation of Phosphines and Phosphine Oxides Phosphinic acids may be prepared by controlled oxidation of primary phosphines, RPH2. In most cases air, oxygen, or hydrogen peroxide is sufficient [162-164] see Eq. (95) ... 

The anaerobic oxidation of phosphines to their oxides by hydroxide ion has been shown to involve the liberation of hydrogen, possibly from the intermediate (21). These oxidations were studied with water-soluble phosphines, since solubility was found to be the main factor controlling the rate of oxidation. The preparation, and detailed n.m.r. spectrum, of PP-dimethyl-P P -diphenyldiphosphine disulphide (22) is a relatively rare example of a study of a mixed disulphide. Many examples of routine oxidation of phosphines to their oxides have appeared. These include the preparation of polyhalogenoarylphosphine oxides using dichromate... 

The explosion hazard associated with the usual laboratory preparation from white phosphorus and alkali may be avoided by an alternative method involving oxidation of phosphine with an aqueous iodine solution [1], The commercial 50% solution reacts violently with oxidants. On heating, it decomposes rapidly above 100°C evolving phosphine, which is liable to explode with air. It is recommended it... 

Finally, Cristau and coworkers have reported on a quite efficient preparation of triphenylphosphine oxide (Figure 2.13) by a similar addition-elimination reaction of red phosphorus with iodobenzene in the presence of a Lewis acid catalyst followed by oxidation of an intermediate tetraarylphosphonium salt.42 This approach holds the potential for the preparation of a variety of triarylphosphine oxides without proceeding through the normally used Grignard reagent. Of course, a variety of approaches is available for the efficient reduction of phosphine oxides and quaternary phosphonium salts to the parent phosphine, including the use of lithium aluminum hydride,43 meth-ylpolysiloxane,44 trichlorosilane,45 and hexachlorodisilane.46... 

Related to this is the mechanism for the catalytic oxidation of phosphines by water. This reaction plays a role in catalysis in water using water-soluble phosphine ligands. 

Rhenium(VII) trioxo-complexes with derivatives of the Klaui ligand (19) are stable in air and organic solvents, but slowly decompose in aqueous solutions yielding perrhenic [Re03(cpCo PO(OR)2 3)] can be prepared from Re20v, perrhenate, or by oxidation of the corresponding Re tricarbonyl complex. Reduction with phosphines in the presence of HBr... 

The latter case has been demonstrated with the reaction of [ReCl3(PPh3)2(CH3CN)] with a large excess of sodium diethyldithiocarbamate which results in sulfur abstraction and in the formation of a mixed phosphine/diethyldithiocarbamato/r/ -thiocarbamoyl complex. For the molecular structure of this compound see formula (225) which represents that of the corresponding rhe-nium(IV) cation which is formed by oxidation of the primarily formed Re complex and contains one rhenium-carbon bond. The formation of thiocarbamoyl compounds seems to be an essential... 

A large number of articles have been devoted to kinetic studies of the oxidation of phosphine 236-243) compositions of phosphine under pressure, which are oxidised by water, have been described by Bushmakin and Frost. ... 

From the same substrates, a different reaction took place when the electron-deficient phosphine was replaced by the electron-rich (p-MeOC6Fl4)3P phosphine. In the presence of this slightly modified catalytic system, the recovery of the organic ligand as a lactone was made possible by oxidation of the intermediate cyclic alkoxycarbene with N-hydroxysuccinimide, a mild oxidant which did not destroy the catalyst (Scheme 10.13) [52]. 

Many pyridine derivatives difficult to make directly from pyridine are readily accessible starting from pyridine A7-oxide, made by oxidation of pyiidine with hydiogen peroxide in acetic acid. As but one example, the nitration of pyndine A7-oxide gives 4-nitropyridine IV-oxide in high yield. Reduction of the >-oxide to the parent pyridine nucleus is readily effected by hydrogenation or reagents, such as PCli or Iriphenyl phosphine. 

A large number of Group VIII metal-dioxygen complexes catalyze the oxidation of phosphine to phosphine oxide or isocyanides to isocyanates by molecular oxygen.6,12,56,140,141 146,184 However, their use as catalysts for the oxidation of alkenes generally leads to the same products as those obtained from free radical chain autoxidations.184,196-198... 

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