Phosphonium phosphines

Rhodium catalysts modified with carboxylated phosphines 45 (Table 3 n=5, n=7)229 and phosphonium phosphines 103 (Table 5 n=2,3,6,10)255 form very active catalytic systems for the hydrogenation of olefins in aqueous/organic two phase systems. 

Cationic heterodinuclear complexes derived from ferrocenyl are not as common as their neutral analogs, and only the pentafluorophenyl derivative [(C6F5)Au (PPh2CH2PPh2CH2Fc)]TfO has recently been prepared by treatment of the phosphonium-phosphine salt [FcCH2PPh2CH2PPh2]TfO with equimolecular amounts of [Au(C[Pg.101]

Rh complexes of composition [Rh(nbd)(33)2]+X containing the phosphonium phosphines 33 (PHOPHOS II, III, VI, X) have been shown to be very active catalysts for the biphasic hydrogenation of n-hexene and maleic acid in water [103, 110]. A definite chain length effect was observed, the system where n = 6 being the most active. The biphasic systems containing longer chain ligands are not well behaved as catalysts since they are prone to formation of stable emulsions which are quite difficult to break. 

An example of the alternative cationic species is provided by [Ph2PCH2NMe3]+G. Baird and coworkers developed this theme in preparing the all-phosphorus cationic phosphonium phosphines [Ph2P(CH2) PMe3]X in = 2, 3, 6, 10 X = NO3, Cl, PFg), to which they gave the trivial names II-, III-, VI-, and X-phosphos. These ligands form water-soluble transition metal complexes such as [(nbd)RhCl(II-phosphos)][PF6]. ... 

Fig. 28 A iV,iV -chelated organoaluminum species with a phosphine-phosphonium/phosphine-stabilized phosphonium moiety...

Robertson, A. L. Seddon, K. R. (Cytec Industries) (2002). Phosphonium phosphinate compounds and their preparation, WO 02/079212 A1 Rogers, R. D., Seddon, K. R. Volkov, S. (Eds.) (2002). Green industrial applications of ionic liquids. Kluwer Academic Publishers, ISBN 1-4020-1136-9, Netherlands Rosatella, A. A., Branco, L. C. Afonso, C. A. M. (2009). Studies on dissolution of carbohydrates in ionic liquids and extraction from aqueous phase. Green Chemistry, 11, 9,1406-1413, ISSN 1463-9262... 

The reaction of potassium hydroxide solution with phosphonium iodide also gives pure phosphine ... 

Towards a simple Lewis base, for example the proton, phosphine is a poorer electron donor than ammonia, the larger phosphorus atom being less able to form a stable covalent bond with the acceptor atom or molecule. Phosphine is, therefore, a much weaker base than ammonia and there is no series of phosphonium salts corresponding to the ammonium salts but phosphonium halides. PH4X (X = Cl, Br, I) can be prepared by the direct combination of phosphine with the appropriate hydrogen halide. These compounds are much more easily dissociated than ammonium halides, the most stable being the iodide, but even this dissociates at 333 K PH4I = PH3 -t- HI... 

Patents on the catbonylation of methyl chlotide [74-87-3] using carbon monoxide [630-08-0] in the presence of rhodium, palladium, and tidium complexes, iodo compounds, and phosphonium iodides or phosphine oxides have been obtained (26). In one example the reaction was conducted for 35... 

Tetrakis(hydroxymethyl)phosphonium Salts. The reaction of formaldehyde (qv) and phosphine in aqueous hydrochloric or sulfuric acid yields tetrakis-(hydroxymethyl)phosphonium chloride [124-62-1/, Albright Wilson s Retardol C, or the sulfate [55566-30-8] (Retardol S), (C4H 2C4P)2SO [55566-30-8]. 

Textile Flame Retardants. The first known commercial appHcation for phosphine derivatives was as a durable textile flame retardant for cotton and cotton—polyester blends. The compounds are tetrakis(hydroxymethyl)phosphonium salts (10) which are prepared by the acid-cataly2ed addition of phosphine to formaldehyde. The reaction proceeds ia two stages. Initially, the iatermediate tris(hydroxymethyl)phosphine [2767-80-8] is formed. 

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]. 

Biocides. Two phosphine derivatives are ia commercial use as biocides. These are tetrakis(hydroxymethyl)phosphonium sulfate [55566-30-8] and tributyl(tetradecyl)phosphonium chloride [8741-28-8]. These compounds are sold by Albright and Wilson Ltd. and EMC, respectively. The preparation... 

Some compounds are named as derivatives of the simple phosphoms hydrides (phosphines). For example, dimethylphosphine [676-59-5], (CH2)3PH triphenylphosphine oxide [791-28-6], (CgH3)3P=0 1,2-dimethyldiphosphine [53684-00-7], CH PHPHCH diethyliodophosphine [20472-47-3], (C2H3)2PI phosphonium iodide [12125-09-6], PH" P tetramethylphosphonium chloride [1941 -19-1], (CH3) P" C1 and phenylphosphonium bromide [55671-96-0], CgH PHjBr-. 

Pure tetrahedral coordination probably occurs only ia species where there are four identical groups and no steric distortions. Both PCU and PBr" 4, present ia soHd phosphoms haUdes, appear to have poiat symmetry. Other species, eg, H PO and POCl, have only slightly distorted tetrahedra. Similar geometries occur ia salts, esters, and other derivatives of phosphoric, phosphonic, and phosphinic acids as well as phosphine oxides and phosphonium salts. 

Phosphine generated by the above procedures is usually contaminated to varying degrees with diphosphine, which renders it spontaneously flammable. Pure phosphine can be produced by hydrolysis of phosphonium iodide [12125-09-6] PH I, which can be made by the action of water on a mixture of phosphoms and diphosphoms tetraiodide [13455-00-0] (71). 

Preparation and Properties of Organophosphines. AUphatic phosphines can be gases, volatile Hquids, or oils. Aromatic phosphines frequentiy are crystalline, although many are oils. Some physical properties are Hsted in Table 14. The most characteristic chemical properties of phosphines include their susceptabiUty to oxidation and their nucleophilicity. The most common derivatives of the phosphines include halophosphines, phosphine oxides, metal complexes of phosphines, and phosphonium salts. Phosphines are also raw materials in the preparation of derivatives, ie, derivatives of the isomers phosphinic acid, HP(OH)2, and phosphonous acid, H2P(=0)0H. 

The addition of alkyl haUdes to phosphines is analogous to the reactions with amines. Because primary phosphonium salts are highly dissociated, the reaction proceeds to the tertiary or quartemary salts. 

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. 

The addition of P—H bonds across a carbonyl function leads to the formation of a-hydroxy-substituted phosphines. The reaction is acid-cataly2ed and appears to be quite general with complete reaction of each P—H bond if linear aUphatic aldehydes are used. Steric considerations may limit the product to primary or secondary phosphines. In the case of formaldehyde, the quaternary phosphonium salt [124-64-1] is obtained. 

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

Phosphonium salts are typically stable crystalline soHds that have high water solubiUty. Uses include biocides, flame retardants, the phase-transfer catalysts (98). Although their thermal stabiUty is quite high, tertiary phosphines can be obtained from pyrolysis of quaternary phosphonium haUdes. The hydroxides undergo thermal degradation to phosphine oxides as follows ... 

Although unsynunetrically substituted amines are chiral, the configuration is not stable because of rapid inversion at nitrogen. The activation energy for pyramidal inversion at phosphorus is much higher than at nitrogen, and many optically active phosphines have been prepared. The barrier to inversion is usually in the range of 30-3S kcal/mol so that enantiomerically pure phosphines are stable at room temperature but racemize by inversion at elevated tempeiatuies. Asymmetrically substituted tetracoordinate phosphorus compounds such as phosphonium salts and phosphine oxides are also chiral. Scheme 2.1 includes some examples of chiral phosphorus compounds. 

Reaction of adsorbed inhibitors In some cases, the adsorbed corrosion inhibitor may react, usually by electro-chemical reduction, to form a product which may also be inhibitive. Inhibition due to the added substance has been termed primary inhibition and that due to the reaction product secondary inhibition " . In such cases, the inhibitive efficiency may increase or decrease with time according to whether the secondary inhibition is more or less effective than the primary inhibition. Some examples of inhibitors which react to give secondary inhibition are the following. Sulphoxides can be reduced to sulphides, which are more efficient inhibitorsQuaternary phosphonium and arsonium compounds can be reduced to the corresponding phosphine or arsine compounds, with little change in inhibitive efficiency . Acetylene compounds can undergo reduction followed by polymerisation to form a multimolecular protective film . Thioureas can be reduced to produce HS ions, which may act as stimulators of... 

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