P—S Bonds

and Raman spectra of compounds in the series OSPFJ, S2PF, SaPFMe , and SgPCCN) have been used to assess force constants using a simplified valence force field.  

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Presumably intermediate thiophosphoric acids are first formed and, indeed, when the hydrolysis is carried out in aqueous NaOH solution at 100°, substantial amounts of the mono- and di-thiophosphates are obtained. P-S bonds are also retained during reaction of P4S10 with alcohols or phenols and the products formed are used extensively in industry for a wide variety of... 

Note It is occasionally recommended that sodium acetate be added to the reagent [2]. Thiophosphate insecticides with a simple P—S bond yield yellow chromatogram zones and those with a P=S double bond yield brown ones on a light brown background [10]. Further treatment of the stained chromatogram with iodine vapors increases the detection sensitivity [7] more than does spraying afterwards with caustic soda solution, which is also occasionally recommended [16, 17, 20, 21]. 

The detection limits for compounds with P=S double bonds are lower than those for substances with single P—S bonds [7]. They are lower on silica gel than on polyamide layers [15] and are, for instance, 10-20 ng substance per chromatogram zone for... 

Demeton-S-methyl sulfone (hRf 0-5), dimethoate (h/ f 5-10), demeton-S-metlq (hRf 20-25), triazophos (h/ f 40-45), azinphos-methyl (hRf 40-45), azinphos-ethj (hRf 50-55), malathion (h/ f 60-65), parathion-methyl (hRf 75-80) and parathioo ethyl (h/ f 80-85) yielded yellow to brown chromatogram zones on a light brown bact ground, with thiophosphate insecticides with P = S double bonds appearing as brow zones and those with single P — S bonds as yellow zones. 

X-ray crystallographic analyses of the structures show that the P-S bond distance vary over one-half of an Angstrom (2.36-2.88 A). The derivatives were generated using procedures similar to those utilized to form pentaoxyphosphoranes with P-N bonds, that is (i) the oxidation of sulfur containing cyclic chlorophosphines with a quinone or (ii) treatment of phosphites with the sulfur-containing diol in presence of N-chlorodiisopropylamine. Two typical examples of these synthetic protocols are shown in Scheme 10. 

Phosphoranyl radicals can be involved [77] in RAFT processes [78] (reversible addition fragmentation transfer) used to control free radical polymerizations [79]. We have shown [77] that tetrathiophosphoric acid esters are able to afford controlled/living polymerizations when they are used as RAFT agents. This result can be explained by addition of polymer radicals to the P=S bond followed by the selective p-fragmentation of the ensuing phosphoranyl radicals to release the polymer chain and to regenerate the RAFT agent (Scheme 41). 

There have apparently been no recent developments in reagents for desulphurizing sulphoxides that use pentavalent phosphorus compounds. Reagents that were reviewed in 1984 include phosphorus pentasulphide, thiophosphoryl bromide, Lawesson s reagent (1), and phosphorus pentachloride in the presence of a trap for CD ions. The traps used included an enamine or an N, JV-dialkylaniline. Presumably, the net effect of this reaction is to generate phosphorus trichloride in situ. The three thiophosphorus reagents obviously function because the P=S bond is some 150 kJ moD weaker than the P=0 bond . 

Considering ions of this type, the question arises, whether the P—S-bond participates in the resonance (I a) and (Ib) with a comparable degree to the PO bond ... 

It should be mentioned, however, that the phosphoramidothioate 202 can undergo hydrolysis by another mechanism which becomes operative above all in polar solvents (e.g. aqueous KOH, and less so in methanol or acetone). P—O bond cleavage occurs, presumably via an addition/elimination mechanism, while the metaphosphorimidate pathway is characterized by P—S bond cleavage. 

The phosphonyl adduct 300 reacted with a dilute solution of anhydrous hydrogen chloride in ethanol or with sodium ethoxide to afford an essentially quantitative yield of the P-N cleaved product 304 with inversion of configuration. Addition of sodium ethoxide to a solution of 304 in methanol resulted in the formation of enantiomerically pure (+)-(.V)-ethyl methyl phenylphosphonate (305). It also reacted quantitatively with methylmagnesium iodide at room temperature to give the product of P-S bond cleavage 306, which upon acid catalyzed methanolysis afforded enantiomerically pure (+)-(R)- methyl methylphenylphosphinate (307) (Scheme 72) [108],... 

Phosphorus acids containing P—S bonds in which the sulfur atom acts as the metal ligating atom also received much attention.243,252,255-261 The commercially available reagents bis(2,4,4-trimethylpentyl)phosphinothioic acid (Cyanex 302) and bis(2,4,4-trimethylpentyl)dithiophosphinic... 

Facile 1,2-addition of the P-Se bond to alkynes occurs in a manner analogous to the addition of the P-S bond (Equation (131 )).299 High regio- and stereoselectivies are observed with phenylacetylene as well as aliphatic alkynes. 

In the imido series, however, the rhenium-nitrogen distances for rhenium(V) average 180.1pm, which is somewhat longer than the average of the values for several rhenium(VII) compounds, 174 pm. The one terminal thio-rhenium bond, 209.2 pm, is significantly shorter than any of the p-S bonds, which average 231pm. 

The hydrolysis of phosmet in an aqueous solution takes place by nucleophilic attack of an OH- group on the phosphorous atom, causing fission of the P-S bond. 

DioxaphosphoIens.—The condensation of a-diketones with tervalent phosphorus compounds has been extended to monothiobenzil.43 Hydrolysis of the resulting adducts (59) gave both P-O and P-S bond fission. Exchange reactions on the benzil-... 

In reactions between methylmagnesium iodide and O-alkyl S-methyl phenylphos-phonothiolate, the mechanistic pathway, i.e. displacement of OR or SMe, depends on the bulk of the group R (Me, Pr1, or menthyl). The bulkier is R, the more extensive is the P—S bond fission.131... 

P—S bond is elongated to 196.5 pm and the P—0(H) bond shortened to 148 pm.164 The structures of the m-vinyl carbonate (136)165 and the cyclic phosphonic anhydride (96)123 have been determined, and for the latter compound the ring was found to be almost planar. A -Ray diffraction data of deoxyuridine phosphate,166 phospholipid multilayers,167 nucleotides,168 and skeletal muscle169 have been analysed. The crystal structure of the phosphazene (137) has been established.170... 

Unlike oxygen derivatives, thioesters of phosphor(III) acids (S-ethyldiphenylphos-phinite, S,S-diethylphenylphosphonite and triethylthiophosphite) undergo electroreduction atDME (dropping mercury electrode) in DME or AN [215]. An irreversible two-electron process results in the P—S bond scission. 

The P—S bond formation of dialkyl (or diaryl) phosphites (21) with disulfide proceeds in an MeCN-NaBr/Et4NCl04-(Pt) system at 20 25 °C, giving phos-phorothiolates (22) in 72 91% yields (Scheme 9) [51]. In this reaction, both sodium iodide and sodium chloride are less effective than sodium bromide. Depending on the nature of the cation, the yields of (22) decrease in the order of Na+ (91%) > K+ (76%) > Li+ (69%) > Et4N+ (46%). 

Following the same route compound 15 was obtained in 56% yield [56] (Scheme 10). Meanwhile, Nifanteev et al. reported the first X-ray structure of a phosphorus(lV) derivative, by describing the solid state structure of 14e, which exhibited the iiii configuration with the four P=S bonds directed toward the molecular cavity [51]. 

The solid state structure of the thiophosphorylated host depicted in Fig. 3 shows unambiguously the all inward orientation of the four P=S bonds [71]. As in the oxidized parent compound 12c, a solvent molecule (acetonitrile) is entrapped in the cavity of the host, and another one is embedded at the lower rim between the four long alkyl chain substituents. 

Two isomers were expected according to the outside or inside orientation of the thiophosphoryl group. Only one isomer was characterized showing the P=S bond directed outside. The new hemicryptophane 22 presents a molecular cavity large enough to complex a toluene molecule as shown in the solid state structure depicted in Fig. 14. The toluene complex is stabilized through Van der Waals and specific r-interactions. 

Because vicinal dibromides are usually made by bromination of alkenes, their utility for synthesis is limited, except for temporary masking of a double bond. Much more frequently, it is desirable to convert a diol to an alkene. Several useful procedures have been developed. The reductive deoxygenation of diols via thiocarbonates was developed by Corey and co-workers.210 Triethyl phosphite is useful for many cases, but the more reactive reductant l,3-dimethyl-2-phenyl-l,3,2-diazaphosphohdine can be used when milder conditions are required.211 The reaction presumably occurs by initial P—S bonding... 

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