Of tertiary phosphines

However, the composition of the mixture can be controlled to some extent by the correct choice of olefin and reaction conditions. For example, the production of tertiary phosphines can be maximi2ed by conducting the reaction at relatively low phosphine pressures, 1.5 MPa (200 psi), and using a 20—30% stoichiometric excess of a straight-chained olefin as in the synthesis of tributylphosphine [988-40-3] by reaction with 1-butene [106-98-9]. 

The mixture can be separated by distillation. The primary phosphine is recycled for use ia the subsequent autoclave batch, the secondary phosphine is further derivatized to the corresponding phosphinic acid which is widely employed ia the iadustry for the separation of cobalt from nickel by solvent extraction. With even more hindered olefins, such as cyclohexene [110-83-8] the formation of tertiary phosphines is almost nondetectable. 

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). 

Figure 1.22 Syntheses of tertiary phosphine complexes of ruthenium.

Figure 1.60 Syntheses of some osmium complexes of tertiary phosphines.

Considerable structural information is available on osmium complexes of tertiary phosphines, arsines and stibines (Table 1.13) [152, 157]. 

A number of tertiary phosphine ligands have been synthesized that also contain an alkene linkage capable of coordinating to a metal. A good example of this kind of coordination is formed in the complex of (tri-o-vinyl-phenyl)phosphine (Figure 2.29) with each alkene acting as a two-electron donor, a noble gas configuration is achieved [67],... 

NMR spectra of tertiary phosphine complexes are often helpful in assigning stereochemistries [114] and two examples of mer-isomers are illustrated here. 

Figure 3.54 The effect of the bulk of tertiary phosphine ligands upon the ease of the formation of...

Mixed mono-complexes can be made (Figure 3.68) the trans-influence of tertiary phosphine on the Pt-S bond is noticeable [121]. 

A number of tertiary phosphine complexes with bulky ligands (Figure 3.80) have modified square pyramidal structures, examples being M(I)3Br2, Pt(II)3Br2 and Pd(III)3Br2 (all X-ray) [136]. 

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

Two papers have appeared on the reactions of halogenophosphines with tervalent phosphorus compounds. In a detailed study of the reactions at 20 °C of a range of tertiary phosphines with phosphorus trichloride, dichlorophenylphosphine, and chlorodiphenylphosphine, it has been shown that, in general, 1 1 adducts are formed, provided that the tertiary phosphine is a good nucleophile. With diphenylchlorophosphine, for example, an adduct (18) is formed with dimethylphenylphosphine, but not with diphenylmethylphosphine, although the relative importance of steric and electronic factors remains to be established. The related reactions of phosphorus trichloride and of dichlorophenylphosphine are much more complex, and the initial crystalline products are not amenable to analysis. The reactions at 280 °C of a similar system have been shown to lead to halogen exchange, e.g. the conversion of (19) to (20). 

One of the advantages of the as molecnlar descriptor to characterise the steric properties of ligands is its generality. This has allowed the placement of tertiary phosphines and NHCs on the same scale. The valnes reported in Fig. 1.18 for two of the most classical phosphines indicate that the less bnUcy PPhj compares with NHCs of intermediate bulkiness, snch as those presenting p-tolyl N-substitnents, while the bulkier PCyj compares with the bulky IPr and SlPr NHCs. Finally, farther refinement of the model was recently disclosed in the form of the dihedral angles ( )j and( )2 (Fig. 1.20). 

Westermark, G., Kariis, H., Persson, 1. and Liedberg, B. (1999) An infrared study on the chemisorption of tertiary phosphines on coinage and platinum group metal surfaces. Colloids and Surfaces A - Physicochemical and Engineering Aspects, 150, 31-43. 

Notably, half of the tertiary product was the telomer 8, which incorporates an additional equivalent of olefin. In contrast, the Pt(0) precatalyst Pt(norbornene)3 (0.2 mol%) gave a 10 1 mixture of tertiary phosphine 9 and telomer 8 over 11 h at 5 5°C in toluene (Scheme 5-10, Eq. 2). The selectivity was higher (>95%) when only the final step [addition of PH(CH2CH2C02Et)2 to ethyl acrylate] was monitored by NMR. In contrast, Pt[P(CH2CH2CF3)3]2(norbomene) did not catalyze addition of PH, to CH2=CHCF3 thus, the olefin must be a Michael acceptor. [11]... 

Nucleophilic Attack at Halogen.- Further applications of tertiary phosphine-tetrahalogenomethane and related "reagents" have been described. The reactions of primary and secondary alcohols with potassium carboxylates in the presence of the triphenylphosphine-tetrachloromethane reagent lead to the formation of esters in good yield. However, application of this procedure... 

X-ray fluorescence spectra of tertiary phosphines (52 Ar = Ph, Y = alkyl) indicated that when the PY2 group is in the best geometry for p-it conjugation the interaction is still only 25% of that of the dimethylamino group.131... 

The A-frame hydride [Pt2H2(/i-H)(/i-dppm)2] undergoes reductive elimination of H2 in the presence of tertiary phosphine ligands, L, to give the platinum(I) dimer, [Pt2HL(//-dppm)2]. Hill and Puddephatt have shown that this occurs via the intermediate [Pt2II2(/i-H)L(//-dppm)2] (14).99 Carbon monoxide reacts rapidly and reversibly with [PtH(/r-PP)2Pt(CO)]+, PP = R2P-CH2-PR2, R = Et or Ph, to give [PtH(/i-PP)2Pt(CO)2]+ and [PtH(CO)(/u-PP)2Pt(CO)2]+, the first reported mixed valence, platinum(0)-platinum(ll) complexes.100... 

The coordination chemistry of tertiary phosphine-functionalized calix[4]arenes have been described.279 Treatment of a bis(diphenylphosphino) or bis(dimethylphosphino) derivative of calix[4]arene with [PtCl2(COD)] leads to the formation of the corresponding dichloroplatinum(II) complex. The related diplatinum(II) species has also been reported with the tetrafunctionalized calix[4]arene.280 The mononuclear derivative is susceptible to oligomerization if the two free phosphine ligands are not oxidized or complexed to another metal center such as gold(I).279 The platinum(II) coordination chemistry of a mono-281 and diphosphite282 derived calix[ ]arene (n = 4 and 6, respectively) has also been described. 

Dimeric zinc complexes of tertiary phosphines, [Zn(PR3)I2]2, are also formed from zinc powder and R3PI2, (R = Me, Et, n-Pr, ra-Bu). The crystal structure of the ethyl derivative demonstrates the dimeric nature of the complexes.295 Metallation of diphenylphosphine with ZnEt2 results in a trimeric species with a Zn3P3 core and bridging diphenyl phosphide ligands. Two protic (HPPh2)... 

Applications of decarboxylation of metal cyanoacetates are currently restricted to derivatives of tin, lead, and copper. Both copper(I) and copper(II) cyanoacetate lost carbon dioxide in dmf at 50° C and formed cyanomethylcopper(I) (15). In the presence of tertiary phosphines, the copper(I) cyanoacetate reaction was reversible [Eq. (35), R = Ph, Et, Bu,... 

OPh, or Ome x = 1, 2, or 3] (47). The carboxylation reaction was favored when the ratio of tertiary phosphine to copper salt was increased to 3 1. This suggests that an intermediate Cu—(C02) complex is not formed. At this ratio the copper complexes are considered coordinately saturated. Carboxylation was also favored when phosphines of high o- donor ability were used. 

Studies of the thermal decarboxylation of phenylpropiolates of copper, tin, and lead parallel those of the corresponding cyanoacetate compounds. Copper phenylpropiolate decarboxylated irreversibly in dmf at 35°C and reversibly in the presence of tertiary phosphines in dmf (52). Triorga-iio(phenylethynyl)tin and -lead compounds, R3MC=CPh [M=Sn, R = Ph or Bu (53) M = Pb, R = Ph (5/)], were isolated when the triorganotin or -lead phenylpropiolates, R3M02CC=CPh, were heated in vacuo. Triphenyllead phenylpropiolate also decarboxylated in refluxing toluene (54). 

Other companies (e.g., Hoechst) have developed a slightly different process in which the water content is low in order to save CO feedstock. In the absence of water it turned out that the catalyst precipitates. Clearly, at low water concentrations the reduction of rhodium(III) back to rhodium(I) is much slower, but the formation of the trivalent rhodium species is reduced in the first place, because the HI content decreases with the water concentration. The water content is kept low by adding part of the methanol in the form of methyl acetate. Indeed, the shift reaction is now suppressed. Stabilization of the rhodium species and lowering of the HI content can be achieved by the addition of iodide salts. High reaction rates and low catalyst usage can be achieved at low reactor water concentration by the introduction of tertiary phosphine oxide additives.8 The kinetics of the title reaction with respect to [MeOH] change if H20 is used as a solvent instead of AcOH.9 Kinetic data for the Rh-catalyzed carbonylation of methanol have been critically analyzed. The discrepancy between the reaction rate constants is due to ignoring the effect of vapor-liquid equilibrium of the iodide promoter.10... 

The reactivity of l-bora-4-phosphacyclohexadienes-2,5 (175) is typical of tertiary phosphines. NMR data bear witness to the absence of a significant interaction between boron and phosphorus and delocalization of the phosphorus lone electron pair. In this respect, they also differ from cyclic compounds containing a P—C—O—B fragment. 

Considerable structural information is available on osmium complexes of tertiary phosphines, arsines and stibines (Table 1.13) [152, 157], Comparison with data (mainly obtained from EXAFS measurements) on osmium diarsine complexes (Table 1.14) shows that as the oxidation state increases, osmium-halogen bonds shorten whereas Os-P and Os-As bonds lengthen. Bond shortening is predicted for bonds with ionic character,... 

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