Phosphines silyl

This chapter will not cover compounds containing heteroatoms hnked to the P and/or N atom of the P-N unit, with the notorious exception of those with N-Si bonds (A/-silyl phosphinous amides) due to its particular relevance in terms of chemical reactivity. 

The JV-silyl phosphinous amides present some particularities in their reactivity that make these compounds worth commenting on separately. They are stable and can be easily prepared in the usual way by reaction of AT-silyl substituted primary amines or hexamethyldisilazane with halophosphanes [48,49,128,129] or byJV-silylation of the appropriate phosphinous amides [72, 107]. The reductive Ph-P bond cleavage in AT-silyl phosphazenes Ph3P=NSiMe3 by the action of sodium is a peculiar example of preparing Ph2PNHSiMe3 [130]. 

The reactivity of N-silyl phosphinous amides versus some of the functional groups in the scheme above has no precedent in nonsilylated analogs. 

The stable P-unsubstituted phosphinous amide H2PN(SiMe3)2 has been shown to suffer the nucleophilic displacement of the disilazane moiety by the action of thiols R-SH giving the phosphinous thioesters R-S-PH2 [13]. For the sake of brevity we shall not comment on other relevant reactions of AT-silyl phosphinous amides, such as the anionic P-silylation [115] and P-alkylation [22], the consecutive dialkylation of PH derivatives [18] and the fluorodesily-lation of P-fluoro-JV-silyl derivatives [140]. 

Scheme 13 NHP-catalyzed P-C cross coupling between silyl phosphines and chloroalkanes...

Phosphasilene 832 is rather labile in solution, and thus derivatives with silyl groups at phosphorous were synthesized and proved to be more stable389,390. The reaction of the silyl phosphines 838 with n-BuLi gave the lithiated species 839, which eliminated LiF upon heating in solution to 60-80 °C and thus liberated the phosphasilenes 840 (equation 290). 

Scheme 11 Reactions of rhenium complexes with silylated phosphine proligands...

Caution. All phosphines are toxic. The diphenylphosphide ion and silyl-phosphine are very sensitive to oxygen and moisture. All operations involving these materials should be carried out in an inert atmosphere and in a good hood. Any excess lithium metal should be destroyed with 1 -propanol in an inert atmosphere. The tetrahydrofuran (THF) should be handled and dried carefully as previously described.5 (See also Synthesis 1 of this volume for dangers involved in drying THF.)... 

Secondary aliphatic phosphines are prepared by other methods, which have been described. Secondary phosphines form molecular addition compounds with boron halides. Dehydrohalogenation of diphenylphosphine-boron triiodide (or diphenylphosphine-boron tribromide) gives the dimeric phosphinoborane. The following method of preparation makes isolation of the intermediate addition compound unnecessary. Reaction of dibutyl(trimethy 1-silyl)phosphine with boron tribromide and ehmination of bromotrimethylsilane gives a dimeric phosphinoborane also. ... 

Caution. [ 2,2-Dimethyl-l-( trimethylsiloxy )propylidene]( trimethyl-silyl)phosphine, a malodorous liquid, is extremely sensitive to moisture and ignites in air. Therefore, all procedures must be carried out under an atmosphere of dry argon in a well-ventilated fume hood. 

Since the H chemical shift values depend strongly on the solvent used, the compounds tri(trimethylsily)phosphine (1) and [2,2-dimethyl-l-(trimethylsiloxy)propylidene] (trimelhyl-silyl)phosphine (11) can best be identified by their coupling constants (1 4.4 cps II 3.8 cps), or by their values (1 - 251 11 + 120). 

Free as well as coordinated IFf-phosphirenes A [3] andB [4], respectively, can be prepared by trapping of transient phosphinidenes [5] with alkynes. By extension of this synthetic route, Niecke et al. prepared the first lff-diphosphirene l Pa [6] by reaction of the chloro(silyl)phosphine 1 with the phosphaalkyne 2 (Scheme 1). Some years later,Mathey et al. [7a] and Streubel et al. [7b] independently reported analogous reactions in the coordination sphere of transition... 

One route to chlorodiphenylphosphine (2) involves the treatment of the silyl-phosphine (4) with chlorine. The disadvantages of this preparation are overcome largely by the use of hexachloroethane, from which (2) can be obtained in good yield. ... 

Carbonyl bis(diphenylphosphide) (21), which is stable at room temperature, has been isolated from the reaction of phosgene with diphenyl(trimethyl-silyl)phosphine at —110 °C. 

The reaction of germyl- or silyl-phosphines with biacetyl leads to cyclic products as well as acyclic derivatives derived from 1,1- and 1,2-addition (see Scheme 1). Condensation of hydrometal-phosphines (39) with biacetyl gives mono-insertion products which cyclize in the presence of HaPtCU into germa-or sila-dioxolan derivatives. 

Here the fragment pattern is the same as before but the condensation reaction is of inverse polarity. Oxazolium ions or zwitterionic munchnones contribute the CNCC chain and tris(trimethyl-silyl)phosphine/arsine contributes the fifth ring member. 

As in the case of monocyclic 1,3-azaphospholes/arsoles (Section 3.16.4.1.4) tris(trimethyl-silyl)phosphine/arsine provides the phosphorus/arsenic ring member by replacing the oxygen atom of an oxazolium ring. 

With tetramethylchloroformamidinum chloride, the reaction with tris(trimethyl-silyl)phosphine (Me3Si)3P provides an elegant route to the air-stable 2-phosphaallyl cation (equation 19)27. 

The reactions of silylphosphines with electron-rich compounds are complex, involving insertion into the Si-P bond as the first step. With carbon dioxide, bis(silyl)phosphines give an equilibrium (equation 20) dominated by the phosphacarbamic acid ester 8 which loses disiloxane if R = 2,4,6-t-Bu3C6H2 (henceforth represented as Ar) to give the phosphaketene 9. This in turn reacts with the silylphosphide 10 to form the 1,3-phosphaallene 11, an analogue of carbodiimides, and also results directly from ArPHSiMe3, n-BuLi and C02 (equation 21)28. 

The synthesis and uses of alkali-metal tetraphosphinoaluminates (103) continue to be of interest, and further examples of the synthesis of silyl-phosphines have appeared.Phenyl(trimethylsilyl)phosphine (104) has... 

For a long time, the only coordination mode known for these complexes was the SBP. The group VI (Cr, Mo, W) pentacarbonyl complexes were the first to be observed, and many others with this geometry were later characterized with different metals (Ru(II), Rh(III), Ir(III), etc) and very varied ligands (alkyl, silyl, phosphine, halide, etc.). In all these complexes, the angle between two basal transoid ligands lies between 160° and 180° three examples are shown in 4-28. 

Germyl- and silyl-phosphines add readily to one of the carbonyl groups of glyoxal to give unstable products which readily lose carbon monoxide, e.g. 

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