Phosphonium complexes

The resulting phosphonium complexes yield very poor rhodium(I) hy-droformylation catalysts (77). 

According to the reaction conditions, phosphonic ester chlorides or phosphonic diesters are obtained directly on alcoholysis of the alkyltrichloro-phosphonium complexes.195... 

Electron-diffraction measurements on trimethyl phosphate are best interpreted by assuming the presence of two rotational isomers the molecular parameters reported are cf(P=0) 1.477 cf(P—O) 1.580 d 0—C) 1.432 A, Z.OPO 105.2°, and Z.POC 118.4°. Thermal condensation reactions between trialkyl phosphates and dialkyl phosphorochloridates give monophosphorus side-products in addition to alkyl pyrophosphates. Detailed examinations of such systems suggest that oxonium-type intermediates such as (111) are involved rather than quasi-phosphonium complexes. 

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... 

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 reaction of higher alkyl chlorides with tin metal at 235°C is not practical because of the thermal decomposition which occurs before the products can be removed from the reaction zone. The reaction temperature necessary for the formation of dimethyl tin dichloride can be lowered considerably by the use of certain catalysts. Quaternary ammonium and phosphonium iodides allow the reaction to proceed in good yield at 150—160°C (109). An improvement in the process involves the use of amine—stannic chloride complexes or mixtures of stannic chloride and a quaternary ammonium or phosphonium compound (110). Use of these catalysts is claimed to yield dimethyl tin dichloride containing less than 0.1 wt % trimethyl tin chloride. Catalyzed direct reactions under pressure are used commercially to manufacture dimethyl tin dichloride. 

Intermediates 18 and 19 are comparable in complexity and complementary in reactivity. Treatment of a solution of phosphonium iodide 19 in DMSO at 25 °C with several equivalents of sodium hydride produces a deep red phosphorous ylide which couples smoothly with aldehyde 18 to give cis alkene 17 accompanied by 20 % of the undesired trans olefin (see Scheme 6a). This reaction is an example of the familiar Wittig reaction,17 a most powerful carbon-carbon bond forming process in organic synthesis. 

This material may be converted directly to a phosphonium salt 1.40 g. (0.0054 mole) of the crude iodide is dissolved in 20 ml. of benzene, and 1.42 g, (0.0054 mole) of triphenylphosphine [Phosphine, triphenyl-] is added. On standing, 2.5 g. (77%) of the triphenylphosphonium salt precipitates as a colorless 1 1 complex with benzene, m.p. 135-137°. Recrystallization from methanol-benzene raises the melting point to 140-142°. Analysis calculated for C28H29PI CeH6 C, 68.23 H, 5.39. Found C, 68.15 H, 5.28. 

Within the wide range of phosphorus compounds described as activating agents for polyesterification reactions,2,310 triphenylphosphine dichloride and diphenylchlorophosphate (DPCP) were found to be the most effective and convenient ones. In pyridine solution, DPCP forms a A-phosphonium salt which reacts with the carboxylic acid giving the activated acyloxy A -phosphonium salt. A favorable effect of LiBr on reaction rate and molar masses has been reported and assumed to originate from the formation of a complex with the A-phosphonium salt. This decreases the electron density of the phosphorus atom... 

Polysulfides have been prepared with many different types of cations, both monoatomic Hke alkah metal ions and polyatomic Hke ammonium or substituted ammonium or phosphonium ions. In this chapter only those salts will be discussed in detail which contain univalent main-group cations although a large number of transition metal polysulfido complexes have been prepared [7-9]. 

At last, barium and calcium complexes of phosphonium bifluorenylide 19 was obtained from the corresponding phosphonium iodide (Scheme 12). The anion displays weak nucleophilicity toward both cations which prefer to coordinate with neutral oxygen of THF and with iodide. Located outside the coordination sphere of the metals, it represents thus the first example of uncomplexed phosphonium diylide [59]. 

As in the preceding case with molybdenum, the spectroscopic and X-ray crystallographic data suggest that the complexes obtained can be described as organometallic analogs of resonance-stabilized phosphonium ylides [74]. 

However an unexpected new cyclic ruthenium phosphorus ylide half-sandwich complex 42 has been obtained by reaction of 41 with dichloromethane as solvent [79]. The cyclisation involves a C-Cl activation and corresponds to the incorporation of the methylene moiety in the P-C bond and to the ortho-metal-lation of one phenyl of the phosphine. An other novel unusual phosphonium ylide ruthenium complex 43 has also recently been described [80]. 

A novel chiral dissymmetric chelating Hgand, the non-stabiUzed phosphonium ylide of (R)-BINAP 44, allowed in presence of [Rh(cod)Cl]2 the synthesis of a new type of eight-membered metallacycle, the stable rhodium(I) complex 45, interesting for its potential catalytic properties (Scheme 19) [81]. In contrast to the reactions of stabihzed ylides with cyclooctadienyl palladium or platinum complexes (see Scheme 20), the cyclooctadiene is not attacked by the carbanionic center. Notice that the reactions of ester-stabilized phosphonium ylides of BINAP with rhodium(I) (and also with palladium(II)) complexes lead to the formation of the corresponding chelated compounds but this time with an equilibrium be-... 

Other works have shown that phosphonium yhdes a-stabilized by a cyano or keto group can behave as ambidentate hgands towards palladium complexes (Scheme 21) [85-89]. 

The bis-phosphonium salt 56 in presence of Pd(OAc)2 leads to the formation of the neutral bis-ylide 57 which reacts with TICIO4 to give the dinuclear cationic complex 58 (Scheme 22) [89,90]. The bis-ylide part, which has potentially two carbons and one oxygen donor atoms, acts as a C,C-chelating ligand through its two soft ylidic carbons. 

Very few examples of bridging non-cyclic methanides of gold are known. Among them the complex 79 has been reported as the result of the reaction of phosphine-phosphonium derivatives with acetylacetonate derivatives of gold(I) [103,104]. The complexes 80 [89,98], already seen in previous paragraphs, cor-... 

The investigations included donor adducts with PO [93], 34,PS [+) [94], 35, and P(NMes ) +) [95], 36. While 34 was only formulated as an intermediate species, the other donor-acceptor complexes, 35 and 36, were characterized by X-ray investigations. To complete this series it may also be compared with bis(ylide)-substituted phosphonium halides [96], 37. For these cases the donors refer to... 

A variety of aromatic phosphonium salts containing methoxy- and dimethylamino-groups has been prepared by the complex salt method ... 

Allylic alkylation of 3-acetoxy-l,3-diphenylpropene by sodium dimethytmalonate, catalysed by the Pd-allyl complex 115, bearing the non-symmetric phosphonium ylide NHC ligand (5 mol%), proceeds to completion with 100% regioselectivity. 

Complexes containing the ylide ligand can be also obtained by reaction of the yellow solution of ylides (prepared by addition of butyllithium to tetrahydrofurane or diethylether solutions of the phosphonium salt) with [AulCfiFs) (tht)]. The weak ligand tht is replaced and the ylide complex is obtained (Equation 3.5) [70]. 

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