Preparation of tertiary phosphines

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

Caution All procedures should be carried out in a well-ventilated hood, and disposable vinyl or latex gloves and chemical-resistant safety goggles should be worn. 

Ensure that all glassware is thoroughly clean and has been dried for at least 4 h in a 120°C oven before use. Assemble glassware while still hot. 

Equip the three-necked flask with a magnetic stirring bar, a glass stopper, a septum and a pressure-equalizing addition funnel. Equip the funnel with the other septum. 

Flush the system with nitrogen before placing at a static pressure. 

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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. 

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]. 

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). 

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. 

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

Preparation by Addition of Tertiary Phosphine Oxides to Acetylene... 

The reaction of alkali metal phosphides with appropriate halides, sultones or cyclic sulfates is a generd method for preparation of a variety of tertiary phosphines useful in aqueous organometallic catalysis. These... 

By far the most ubiquitous intermediates in synthesis of this class of phosphines are the alkali metal phosphides which can be prepared by either the KOH/DMSO method, by reaction of tertiary phosphines or chlorophosphines with alkali metals, or in the reaction of BuLi with appropriate secondary or tertiary phosphines. A number of the ligands in Figures 6 and 7 were prepared this way (60-69,72-74). 

The procedures described below have consistently given stable, crystalline products for a number of tertiary phosphine copper hydride complexes. These complexes can be prepared by the careful reaction of lithium tetrahydrido-aluminate(l-) with tertiary phosphine copper halide complexes. The reactions are run in etheral solvents under an inert atmosphere. The resultant products are... 

The alkylation of tertiary phosphines is, in general, compatible with elaborate structures bearing various functions or chiralities, as illustrated by the preparation of a phosphonium salt (18), intermediate in the synthesis of pseudomonic acid248 (reaction 17). For the preparation of dialkylphosphonium salts, diphenylphosphine can be directly alkylated, but it is more advantageous to use triphenylphosphine as the starting material,... 

Following the aforementioned pioneering work, many other organometallic complexes of nickel(II) were prepared using different synthetic procedures. Complexes containing one molecule of tertiary phosphine were prepared using methods similar to that reported in equations (142) and (143) and Scheme 13.1193-11951219-1223 All of these diamagnetic compounds have the square planar structure exemplified by (155).1193... 

Other air stable complexes of tertiary phosphines may be prepared from Re(NNC(0)Ph)Cl2(PPh3)2 by procedures that are very similar to that presented above for Re(N2)(PMe2Ph)4Cl. The original literature in references 10-12 represent appropriate leads to a number of these useful reactions.13... 

The trans- [Rh(PR3)2Cl(CO)] complexes were prepared by treating [RhCl(CO)2]2 under nitrogen in chloroform solution with 2 equiv of tertiary phosphine per rhodium atom. The only side product was carbon monoxide so that purification by recrystallization from ethanol or ethanol-chloroform was relatively simple. The lower-molecular-weight trialkylphosphine and higher-molecular-weight triarylphos-phine complexes were orange, viscous oils the others were cream-colored, low-melting crystalline solids. 

Barton and coworkers exploited this strategy in the preparation of overcrowded ethylenes456 usually the desulfurization of a thiirane is accomplished by one equivalent of tertiary phosphine, mainly triphenylphosphine. However, spontaneous loss of sulfur from thiiranes substituted by aryl or halogen has sporadically been reported. Huisgen has reviewed this subject455 and performed many kinetic studies. He found that the desulfurization step can be accomplished by catalytic thiolates and also by thiobenzophenone or other thioketones, although in this case the reaction is slower (equation 131). 

The synthesis and reactivity of a series of nickelacyclopentane compounds with a range of tertiary phosphine ligands was reported by Grubbs et ol. Compounds of type 69 were prepared by the reaction of 1,4-dilithiobutane with the appropriate dichlorobis(tertiaryphosphine)nickel(II) complex, and isolated as yellow crystals in ca. 40% yield78 (dppe = bis(diphenyl) (phosphinoethane). 

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