A-silylated phosphine

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. 

Chlorosilanes are also very reactive towards the a-metallated phosphine boranes leading to a-silylated phosphine boranes (Scheme 4.38). 

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]. 

Preparation of ethyl methyl(2-carbomethoxy-3-phenylpropyl)phosphinate — Addition of a monobasic phosphinous ester to an unsaturated ester in the presence of a silylating agent... 

A platinum(H) complex has been prepared with a phosphine ligand chelated with a silyl. The complex (141) is formed by treating Pt(cod)2 with Ph2PCH2CH2SiHR R" (equation 423).1412 When R = R", racemic and meso diasteromers are formed in varying ratios consistent with asymmetric induction during stepwise chelation. The complexes can be used for asymmetric hydrosilylation.1413... 

Two recently developed coupling reactions of an alkene (R1CH2CH=CH2), an aldehyde (R2CHO), and a silyl triflate (R33SiOTf) yield an allylic (66) or homoallylic (67) alcohol (in protected form).188 Employing nickel-phosphine catalysts, either product can be selected by small changes in the phosphine component. A mechanism distinct from that of Lewis acid-catalysed carbonyl-ene reactions is proposed and discussed. 

Three-component aldol synthesis.1 This rhodium carbonyl can promote aldol coupling of enol silyl ethers with aldehydes or ketones. It can also effect coupling of an enone, an aldehyde, and a trialkylsilane to provide a silyl aldol. In the case of an enolizable aldehyde, yields are improved by addition of a phosphine ligand such as... 

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.)... 

The only example of Si H M agostic interaction supported by a phosphorus bridge was discovered by Driess et al. in the complexation of a silylated triphosphine ligand to a chromium tricarbonyl complex [Eq. (20)].143,144 A bigger metal (M = Mo) or smaller substituent at silicon (R = Ph) leads to the normal triphosphine complexes. The presence of a Si H "M interaction in 59 is deduced from the lack of C3 symmetry (evident from NMR), the red shift of the IR band for the coordinated Si-H bond (1994 cm-1 vs. 2142 cm-1), and the observation of a reduced Si-H coupling (135.7 Hz for the coordinated Si-H bond vs. 210.9 and 228.6 Hz for the free Si-H bonds). The X-ray structure determination of 59 shows that one of the phosphine ligands is tilted away from the chromium atom so that the... 

Many other reports of ligand libraries for specific catalytic applications have been reported. Among them, Gilbertson and co-workers reported a chiral phosphine library, tested in the rhodium-catalyzed asymmetric hydrogenation of an enamide (158,159), and a similar library for the palladium-catalyzed allylation of malonates (160, 161) Hoveyda and co-workers (162, 163) reported a chiral Schiff base library, screened in the titanium-catalyzed opening of epoxides with (TMSCN) (trimethyl silyl cyanide) ... 

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. 

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... 

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