Preparation phosphines, tertiary

The preparation of tertiary phosphines by this approach proceeds with fewer complications than does the preparation of secondary phosphines, although the reaction remains useful for secondary phosphines. 

The simple sulfide AU2S is a very insoluble, luminescent compound whose coordination chemistry is unknown.184,185 Better characterized complexes can be prepared with tertiary phosphine-gold(I) units (equation 17 R = Me, Et, Ph).186-188 In [S(AuPPh3)2], each gold(I) centre has linear stereochemistry with angle AuSAu = 88.7(1)°.188... 

Preparation of tertiary phosphines 2.1 Synthesis from organometallics and electrophilic phosphorus compounds... 

Table 2.2 Some metal phosphides that can be prepared from tertiary phosphines...

An additional approach toward the preparation of tertiary phosphines is by the reduction of more highly coordinated phosphorus species, particularly phosphine oxides [0=PR3] and phosphine sulfides [S=PR3] (see Section 5.2), but also phosphonium salts [ILtP+X"] and quasiphosphonium salts [R3P-YR +X ] (see Sections 4.2 and 4.4). Numerous reducing agents have been used to accomplish these conversions, including hexachlorodisilane [CbSi-SiCft], trichlorosilane [HSiCft], phenylsilane [PhSiHs], and lithium aluminum hydride [LiAlH4]. 

Secondary aromatic phosphines can be prepared from tertiary phosphines by cleavage with sodium in liquid ammonia, and the detailed preparation of diphenylphosphine by this method has been reported. Diphenylphosphine has also been prepared by the reaction of chlorodiphenylphosphine with alkali metals or with lithium tetrahydroaluminate. This phosphine has been also obtained from diphenyltrichlorophosphorane or tetraphenyldiphosphine-disulfide with lithium aluminum hydride. A faster and easier method of preparation, which gives equally high yields, consists in the cleavage of tri-phenylphosphine with lithium metal in tetrahydrofuran, followed by hydrolysis of lithium diphenylphosphide with water to generate the phosphine. ... 

This is a very useful route for the preparation of phosphines, especially chiral phosphines. Tertiary phosphine oxides (and sulfides) and phosphonium salts are often precursors of choice in these reduction procedures. The following sections highlight reagents and reaction conditions in forthcoming sections further examples will be given. 

Interest in the preparation of tertiary phosphine oxides by this route has recently been revived by several groups of workers with the result being considerable improvement in the synthesis of tertiary phosphine oxides by this method (Kirsanov and coworkers) (for a summary see Table 1). 

The reaction between white phosphorus, MesSiCl, and a mixture of sodium and potassium in either mono- or di-glyme as solvent provides a simple method for preparing the tertiary phosphine (Me3Si)3P. Scrambling reactions of the latter with MeiGeCl and Me3SnCl lead to all ten possible products, which can be identified by P n.m.r. spectroscopy. ... 

For the last few year the catalytic asymmetric synthesis of tertiary phosphines has attracted the attention of many chemists. Interesting results were published in many articles and reviews [109-115]. Catalyzed by transition metals, asymmetric phosphination of secondary, racemic phosphines with aryl halides or triflates to prepare a tertiary P-stereogenic phosphines with control of the stereochemistry at the phosphorus atom is shown in Scheme 62. 

Scheme 91 Enzymatic preparation of tertiary (R)- or (S) phosphine oxides...

In conclusion, we have presented a new method for the preparation of tertiary phosphine oxides of the type R2R P0 from a secondary phosphine oxide and an alkyl halide with excellent yields, using phase transfer catalysis. Furthermore, this method can be successfully applied to the chemical modification of soluble and cross-linked polystyrenes. Examination of the molecular weights, M, and of the composition of the modified polymers indicates that no side reactions or degradation occur in the conditions we have used. Further work in this field is in progress. 

Phosphonium salts are readily prepared by the reaction of tertiary phosphines with alkyl or henzylic haHdes, eg, the reaction of tributylphosphine [998-40-3] with 1-chlorobutane [109-69-3] to produce tetrabutylphosphonium chloride [2304-30-5]. 

RM can be a traditional Grignard reagent or an organolithium, 2inc, aluminum, or mercury compound. The Grignard route is employed commercially for production of tertiary phosphines, even though these reactions are subject to side reactions. Yields are often low, eg, 40—50% for (C4H )2P prepared via a Grignard reaction (18). A phosphoms—carbon bond can form from the metathetical reaction of a phosphoms haUde and a pseudohaUde salt. 

Alkylation of phosphines by alkyl hahdes exhibits reactivity relative to the base strength, ie, PH is the least reactive and tertiary phosphines the most. This reactivity reflects the difficulty in using alkylation to prepare anything except quaternary phosphonium hahdes. 

Phosphonium salts may also be prepared by the addition of tertiary phosphines to carbonyl compounds or olefins (97). 

The first important lead toward the application of ylides as an initiator came from the observations of Zweifel and Voelker [47] in 1972. In their experiment, these authors polymerized lactones or unsaturated compounds initiated by phosphorus ylides prepared directly from tertiary phosphines or similar compounds. 

A considerable number of the tertiary phosphine and arsine complexes of iridium(III) have been synthesized [4, 8] they generally contain 6-coordinate iridium and are conventionally prepared by refluxing Na2IrCl6 with the phosphine in ethanol or 2-methoxyethanol [154]... 

The tertiary phosphine complexes are the most important zerovalent compounds. They are frequently prepared by reductive methods, often using the phosphine as the reducing agent [43], e.g. 

Dihydrides are more difficult to prepare but are most easily obtained with very bulky tertiary phosphines [101a]... 

The most important of the tertiary phosphine complexes of platinum(IV) are Pt(QR3)2X4, generally prepared by halogen oxidation [174] of cis- or trans-Pt(QR3)2X2 (Q = P, As, R = alkyl Q = Sb, R = Me), since direct reaction of the platinum(IV) halides with the ligands leads to reduction. Once made, the platinum(IV) compounds are stable to reduction ... 

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