Phosphine Oxides, Sulphides, and Selenides

Phosphine oxides have fallen upon hard times, judging by the current literature, which this year has provided fewer publications on the subject than were reviewed in the first volume of this series A timely reminder that the subject is nevertheless alive comes from the thorough reviews of phosphine oxides, sulphides, selenides, and tellurides in the new edition of Kosolapolf s compilation. These chapters are likely to be of particular value to chemists requiring a quick guide to known structures and their preparation. 

The synthesis of chiral phosphine oxides has stimulated effort in a number of laboratories in recent years. An elegant new approach to the problem involves the use of sugar-derived phosphorus heterocycles. These are 1,3,2-dioxa-phosphorinan-2-ones, such as (1), formed from glucosides and various phosphonic dihalides, such as (2). The preparation of chiral phosphine oxides 

Another route to chiral phosphine oxides begins with tertiary phosphine sulphides, which, on treatment with acidic dimethyl sulphoxide, yield the corresponding phosphine oxides. When chiral phosphine sulphides (4) are used the products are oxides of inverted configuration. 

Details have appeared of the preparation of phosphine oxides from phosphonic or phosphinic esters using hydride sources and alkyl halides. The method is claimed to be convenient and give good yields, and is illustrated by the preparation of benzyldibutylphosphine oxide (5). 

Syntheses in the phospholan series include the oxides (6), (7), and (8). Of these, l-methyl-3-phospholanone 1-oxide (6) has been studied in considerable detail. It is a keto-enol mixture, and the reactions outlined here reflect the reactivity of the hydrogens at C-2. The isomeric oxides (7) and (8) were prepared by photochemical methods. The A -phospholen 1-oxide (8) undergoes an unusual photochemical reduction in alcoholic solution (see ref. 41). 

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A"-Ray structure determinations (see Chapter 11 for details) have been reported for triphenylphosphine oxide, tri-o-tolylphosphine oxide, sulphide, and selenide, and for cw-2,2,3,4,4-pentamethyl-l-phenylphos-phetan-1-oxide (5). Electron spectroscopic studies of phosphorus oxychloride and thiophosphoryl chloride in the gaseous state, and n.m.r., i.r., and u.v. spectra of phosphine sulphides have appeared. Dipole moments have been used to define the stereochemistry of 2-cyanoethylphosphine oxides, such as (6), which is shown in its preferred conformation. 

Restricted rotation has been observed in tris-o-tolylphosphine sulphide and selenide (39). The spectrum of the selenide shows two methyl environments in the ratio 2 1 at 30 °C but the methyl signals of the sulphide resolved to this pattern only upon cooling the sample. The corresponding oxide and the parent phosphine showed only one methyl environment down to — 60 °C. Y-Ray diffraction of the selenide showed that the methyl group on one aryl group is directly behind the phosphorus atom in the crystal, as shown in (39). 

Includes bibliographical references and indexes. Contents v. 1. Primary, secondary, and tertiary phosphines, polyphosphines, and heterocyclic organo-phosphorus(III) compounds—v. 2. Phosphine oxides, sulphides, selenides, and tellurides—v. 3. Phosphonium salts, ylides, and phosphoranes. 

Volume 2 covers phosphine oxides, sulphides, selenides and tellurides. 

Hartley, F. R., ed. The Chemistry of Organophosphorus Compounds, Vol. 2. Phosphine Oxides, Sulphides, Selenides and Tellurides. John Wiley Sons Chichester ... 

H nmr studies in non-polar solvents have shown that whereas the sulphide and selenide of the heterocyclic system (224) involve intramolecular coordinative interactions between tin and sulphur or selenium, the related phosphine oxide prefers to bind intermolecularly. In the solid state, a similar situation applies.Structural studies of adducts of triphenylphosphine oxide with monoorganotrichlorostannanes have also been reported. Various types of phosphine oxides are able to complex alkali and alkaline earth metal cations, and to facilitate their transfer across aqueous/organic interfaces.Organogallium complexes of phosphine oxide ligands have been isolated from the reactions of organogallium peroxo derivatives with phosphines. ... 

Phosphorus (v) Compounds. Dipole moments for a series of phosphine and arsine chalcogenides point to the arsines being of greater polarity and for polarity to increase generally in the order oxide < sulphide derived bond moments are discussed in terms of the relative amounts of double-bond character. Displacement reactions in the systems RsM C BFj-RslVFC), where R1 and R2 = Me, Et, or Pr and M1 and M2 = N,P, or As, can be followed by n.m.r. spectroscopy, showing... 

Of an equally novel nature is the thermally catalysed rearrangement of the phosphine oxides (or sulphides, or selenides) 388 into the equilibrated system also containing the corresponding 389 and which, on addition of an alcohol, gives rise to the phosphinic esters 390 ... 

All the tertiary phosphines are highly refractive liquids, lighter than and insoluble in water. Those of low molecular weight readily absorb oxygen from the air, yielding oxides they also have indescribably unpleasant odours. The compounds combine with sulphur, selenium and carbon disulphide, forming respectively sulphides, selenides and compounds of the type... 

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