Phosphine sulphides

The tertiary phosphine sulphides, R3PS contain a single terminal P=S linkage. One of the simplest and best methods of preparation is the direct reaction of the tertiary phosphine with elemental sulphur (6.74). The reaction, normally exothermic, is carried out in benzene or carbon disulphide with moderate 

Good yields of tertiary phosphine sulphides can be obtained by reacting PSCI3 with organoalu-minium or organoalkali compounds. 

A lengthening of the P=S bond usually occurs on complex formation. 

With alkyl halides, phosphonium compounds can be obtained. 

Tertiary phosphine sulphides are thermally less stable than the corresponding oxides, reflecting the lower dissociation energy of P=S compared to that of P=0, and the corresponding lower n bond order in the sulphur compound. 

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Oxidation and other products from the reaction of thiones and phosphine sulphides with metal salts and halogens. E. W. Ainscough and A. M. Brodie, Coord. Chem. Rev., 1978, 27, 59-86 (103). 

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. 

C. By Oxidation.—This year s literature has been notable for attempts to study the details of certain phosphine oxidation reactions. In one such investigation nitric acid was found to oxidize phosphines, or phosphine sulphides, to phosphine oxides with inversion of configuration at phosphorus, whereas dinitrogen tetroxide, in the absence of acid, was found to oxidize the same compounds with predominant retention. The partial racemization observed with the latter reagent was probably due to the racemization of the oxides, since methylphenyl-n-propylphosphine oxide... 

Two contrasting conclusions have been reported in the reactions of lithium aluminium hydride in THF with phosphine oxides and phosphine sulphides respectively. The secondary oxide, phenyl-a-phenylethylphos-phine oxide (42), has been found to be racemized very rapidly by lithium aluminium hydride, and this observation casts some doubt on earlier reports of the preparation of optically active secondary oxides by reduction of menthyl phosphinates with this reagent. A similar study of the treatment of (/ )-(+ )-methyl-n-propylphenylphosphine sulphide (43) with lithium aluminium hydride has revealed no racemization. These results have been rationalized on the basis of the preferred site of attack of hydride on the complexed intermediate (44), which, in the case of phosphine oxides (X = O), is at phosphorus, and in the case of the sulphides (X = S), is at sulphur. Such behaviour is comparable to that observed during the reduction of phosphine oxides and sulphides with hexachlorodisilane. ... 

The dipole moment of tributylpliosphine varies from 1.49 to 2.4 D according to the solvent used. Inductive effects in phosphines have been estimated by comparing the calculated and observed dipole moments, and the apparent dipole moment due to the lone electron pair on phosphorus has been estimated. A method of calculating the hybridization of the phosphorus atom in terms of bond angles is suggested which leads to a linear relationship between hybridization ratio and lone electron pair moment. The difference between experimental and calculated dipole moments for para-substitued arylphosphines, phosphine sulphides, and phosphinimines has been used to estimate mesomeric transfer of electrons to phosphorus. 

Bis(trimethylsilyl)peroxide (1) can be used to produce phosphine oxides stereospecifically from either phosphines (with retention) or phosphine sulphides (with inversion).1 A variety of organoelement substituted pentadienes, including the phosphine oxides (2) and (3),... 

By Addition ofP—H to Unsaturated Compounds. This route continues to be exploited for the synthesis of polydentate tertiary phosphine ligands. Thus base-catalysed addition of diphenylvinylphosphine to the secondary phosphine (25) affords (26).23 Neopentylpolytertiaryphosphines, e.g. (27), have been similarly prepared24 by addition of primary or secondary phosphines to vinylphosphines (or the related phosphine sulphides, followed by a desulphurization step). 

Details have appeared of the conversion of chiral phosphine sulphides (20) into the corresponding inverted oxides, and a rationalization of the stereochemistry has been... 

Migration of sulphur from one phosphorus to another has been observed39 when the sulphide (45) is heated. The intermediates (46) and (47) have been detected. Debenzyl-ation of the phosphine sulphide (48) has been shown to be accompanied by a desulphuration, which is believed to result from the interaction of (49) with alkaline DMSO.40... 

Further examples of deoxygenation of epoxides by phosphine sulphides or selenides have appeared,41 as shown in Scheme 6 for simple epoxides (50). Incorporation of phosphorus into a five-membered ring appears to be responsible for the relatively rapid deoxygenations by the phosphole and A3-phospholen derivatives.41... 

Ethyl methyl ethylphosphonothionate (94 X = S) and the 4-methyl-l,3,2-dioxaphosphorinans (95 X = S R = OMe or NMe2) are oxidized with 90% H202 to the phosphoryl analogues with net retention of configuration phosphine sulphides, in contrast, are oxidized with inversion and racemization.64... 

The molecular ion appears to retain its cyclic structure, but several ions with two or three phosphorus atoms can be detected.192 The fragmentation patterns of a number of dialkylphosphines (157) show initial loss of an alkyl group as a neutral particle formed by the transposition of hydrogen.193 Some six-membered cyclic phosphites (158 X = OEt, OPh, or Cl) have been studied.194 The mass spectra of a wide variety of phosphine sulphides (159 Z = Ph, Me, CH2Ph, COPh, NH2, N=CHPh, or... 

Tris(trimethylsilyl)silane reacts with phosphine sulfides and phosphine selen-ides under free radical conditions to give the corresponding phosphines or, after treatment with BH3-THF, the corresponding phosphine-borane complex in good to excellent yields (Reaction 4.45) [82]. Stereochemical studies on P-chiral phosphine sulphides showed that these reductions proceed with retention of configuration. An example is given in Reaction (4.46). 

Tris(aziridinyl)-para -benzoquinone Tris(l-aziridinyl)phosphine-oxide Tris(l-aziridinyl)phosphine-sulphide see Thiotepa)... 

Phosphine sulphides and thiophosphates have been converted into phosphine oxides and phosphates, respectively, by reaction with dimethyldioxirane (11). ... 

Optically active secondary and tertiary phosphine sulphides have been prepared by the reaction of optically active phosphinodithioates (12) with butyllithium followed by treatment with electrophiles. Compounds (13, R=t-Bu, E=H) and (13, R=1-naphthyl, E=H) prepared in this study are claimed to be the first reported examples of optically active secondary phosphine sulphides. 

Aliphatic and aromatic thiols have been added to (5) -methylphenylvinylphosphine oxide (84) to provide optically active P-alkylthio- and p-arylthioethylphenylphosphine oxides (85).The reaction of the phosphine sulphide (86) with tetrachloro-o-benzoquinone gives (87) which undergoes further rearrangement. ... 

The behaviour of tert-butylphenylphosphinothioic chloride towards Ag contrasts markedly with that of the corresponding iodide. In MeN02, the chloride is unreactive, but the iodide affords a mixture of phosphorus-containing products. Tert-butylphenylphosphine sulphide was notable in its absence. The phosphine sulphide (253) was obtained when the reaction involving the iodide was carried out in anisole. Both the iodide, preparable from the mixed anhydride (254), and the latter itself, react with MeOH-Ag to give Q-roethyl tert-butylphenylphosphinothioate with configurational inversion. The mixed anhydride (254), which also... 

The boron trihalide complexes with a number of phosphine sulphides and selenides can be isolated for the chloride, bromide, or iodide but, consistent with its reduced Lewis acidity, the trifluoride does not react.600 Alkyldithio-phosphonic acids give tin, lead, and mercury derivatives such as Me3SnSP-(S)FEt, Pb[SP(S)FMe]2, and MeHgSP(S)FMe, which are monomeric in solution, and there is n.m.r. evidence for a bidentate phosphonate group in the tin compound.601 Vanadyl chelates of alkoxy-ethyl and alkoxy-phenyldi-thiophosphonates (87) have been synthesized and e.s.r. measurements... 

It was shown that dipiperidyl sulphide is converted into tris(dimethyl-amino)phosphine sulphide on standing in HMPA overnight, and that the overall reaction of piperidyl-lithium with elemental sulphur may therefore be written ... 

The reaction of thiobenzophenone with tri-n-butylphosphine at 100 °C gives 1,1,2,2-tetraphenylethane, tetraphenylethylene, and the phosphine sulphide. A similar reaction occurs with dibenzocyclopentadienethione. ... 

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. 

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