Catalysts tertiary phosphine

Rhodium Ca.ta.lysts. Rhodium carbonyl catalysts for olefin hydroformylation are more active than cobalt carbonyls and can be appHed at lower temperatures and pressures (14). Rhodium hydrocarbonyl [75506-18-2] HRh(CO)4, results in lower -butyraldehyde [123-72-8] to isobutyraldehyde [78-84-2] ratios from propylene [115-07-17, C H, than does cobalt hydrocarbonyl, ie, 50/50 vs 80/20. Ligand-modified rhodium catalysts, HRh(CO)2L2 or HRh(CO)L2, afford /iso-ratios as high as 92/8 the ligand is generally a tertiary phosphine. The rhodium catalyst process was developed joindy by Union Carbide Chemicals, Johnson-Matthey, and Davy Powergas and has been Hcensed to several companies. It is particulady suited to propylene conversion to -butyraldehyde for 2-ethylhexanol production in that by-product isobutyraldehyde is minimized. 

The search for catalyst systems which could effect the 0x0 reaction under milder conditions and produce higher yields of the desired aldehyde resulted in processes utilizing rhodium. Oxo capacity built since the mid-1970s, both in the United States and elsewhere, has largely employed tertiary phosphine-modified rhodium catalysts. For example, over 50% of the world s butyraldehyde (qv) is produced by the LP Oxo process, technology Hcensed by Union Carbide Corporation and Davy Process Technology. 

In this case, yields >95% of the tertiary phosphine are obtained. Tributylphosphine is readily converted to tetraalkylphophonium salts by reaction with an alkyl haUde. These compounds are used commercially as biocides and phase-transfer catalysts. 

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 ... 

A Belgian patent (178) claims improved ethanol selectivity of over 62%, starting with methanol and synthesis gas and using a cobalt catalyst with a hahde promoter and a tertiary phosphine. At 195°C, and initial carbon monoxide pressure of 7.1 MPa (70 atm) and hydrogen pressure of 7.1 MPa, methanol conversions of 30% were indicated, but the selectivity for acetic acid and methyl acetate, usehil by-products from this reaction, was only 7%. Ruthenium and osmium catalysts (179,180) have also been employed for this reaction. The addition of a bicycHc trialkyl phosphine is claimed to increase methanol conversion from 24% to 89% (181). 

Tertiary phosphine complexes [42] are the most important rhodium(I) compounds. RhCl(PPh3)3 ( Wilkinson s compound ), a hydrogenation catalyst, is the most important, but they exist in a range of stoichiometries. Synthesis follows several routes ... 

Coordination-catalyzed ethylene oligomerization into n-a-olefins. The synthesis of homologous, even-numbered, linear a-olefins can also be performed by oligomerization of ethylene with the aid of homogeneous transition metal complex catalysts [26]. Such a soluble complex catalyst is formed by reaction of, say, a zero-valent nickel compound with a tertiary phosphine ligand. A typical Ni catalyst for the ethylene oligomerization is manufactured from cyclo-octadienyl nickel(O) and diphenylphosphinoacetic ester ... 

A particularly useful phosphine ligand for the cobalt carbonyl catalyst is a bicyclic tertiary phosphine available from 1,5-cyclooctadiene, phosphine, and an a-olefin ... 

Cobalt carbonyl complexes with tertiary phosphine ligands are not volatile. This makes possible a distillative separation of the reaction products from the cobalt catalyst system (Fig. 5). 

Ph3P)4Pd and certain Pd(II) complexes in the presence of an excess of a tertiary phosphine also function as active catalysts (128). This indicates that palladium species may have potential provided they are protected from destructive reduction by the choice of suitable ligands. A complex species [(Ph3P)2Pd]jf gradually forms in the PhjP—Pd metal mixture ( 28). 

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... 

Active catalysts for dinitrogen activation have been prepared by reduction at a mercury pool of M0CI5 in basic methanolic solutions containing MgCl2, phospholipids, and various tertiary phosphines.319 The turnover number reached several hundreds per Mo center. Both ammonia and hydrazine were formed in a ratio of about 1 10. 

Compounds (L)AuR have been used as precursor molecules for the in situ preparation of the strong nucleophiles [(L)Au]+ X- by treatment with strong acids HX (X = CF3S03, CF3C02, BF4, PF6, SbF6 etc. L = tertiary phosphine R = alkyl) in polar solvents (Equation (2)). The solutions are used as catalysts for the activation of alkenes and alkynes for addition of water, alcohols, and amines (Sections 4 and 10). 

Amphiphilic resin supported ruthenium(II) complexes similar to those displayed in structure 1 were employed as recyclable catalysts for dimethylformamide production from supercritical C02 itself [96]. Tertiary phosphines were attached to crosslinked polystyrene-poly(ethyleneglycol) graft copolymers (PS-PEG resin) with amino groups to form an immobilized chelating phosphine. In this case recycling was not particularly effective as catalytic activity declined with each subsequent cycle, probably due to oxidation of the phosphines and metal leaching. 

The cationic complexes Rh(diene)L >+ (L is a tertiary phosphine, phosphite, or arsine) were reported by several groups in 1969- 1970 (7, p. 270), but Osborn et al. 129-132) first reported on their potential for hydrogenation of olefins, acetylenes, and ketones. Full details on these systems have now appeared 133-135), and the important equilibria governing the active catalysts are given in Eqs. (23)-(25). An important difference from... 

For example, direct treatment of red phosphorus with potassium hydroxide in a mixture of dioxane and water with a phase-transfer catalyst (benzyltriethylammonium chloride) allows direct reaction with primary haloalkanes to form the trialkylphosphine oxide in moderate (60-65%) yield.1415 Allylic and benzylic halides are similarly reported to generate the corresponding tertiary phosphine oxides. When the reaction is performed with a,(o-dihalides, cyclic products are generated only with four- and five-carbon chains the third site... 

Following Wilkinson s discovery of [RhCl(PPh3)3] as an homogeneous hydrogenation catalyst for unhindered alkenes [14b, 35], and the development of methods to prepare chiral phosphines by Mislow [36] and Horner [37], Knowles [38] and Horner [15, 39] each showed that, with the use of optically active tertiary phosphines as ligands in complexes of rhodium, the enantioselective asymmetric hydrogenation of prochiral C=C double bonds is possible (Scheme 1.8). 

The binuclear precursor (di-,u-chloro-bis-[ /4-2,5-norbomadiene]-rhodium(I)) = [(Rh(NBD)Cl]2 is well suited for the in-situ preparation of a variety of homogeneous hydrogenation catalysts, if tertiary phosphines (here PMe3, PMe2Ph,... 

During the late 1960s, Homer et al. [13] and Knowles and Sabacky [14] independently found that a chiral monodentate tertiary phosphine, in the presence of a rhodium complex, could provide enantioselective induction for a hydrogenation, although the amount of induction was small [15-20]. The chiral phosphine ligand replaced the triphenylphosphine in a Wilkinson-type catalyst [10, 21, 22]. At about this time, it was also found that [Rh(COD)2]+ or [Rh(NBD)2]+ could be used as catalyst precursors, without the need to perform ligand exchange reactions [23]. 

Aqueous two-phase hydrogenations are dominated by platinum group metal catalysts containing water-soluble tertiary phosphine ligands. The extremely stable and versatile N-heterocyclic carbene complexes attracted only limited interest, despite the fact that such complexes were described in the literature [62-65]. Recently, it was reported that the water-soluble [RuXY(l-butyl-3-methylimi-dazol-2-ylidene) ( 76-p-cymene)]n+ (X=Ch, H20 Y = C1-, H20, pta) complexes preferentially hydrogenated cinnamaldehyde and benzylideneacetone at the C = C double bond (Scheme 38.5) with TOF values of 30 to 60 h 1 in water substrate biphasic mixtures (80 °C, lObar H2) [66]. 

In the sixties it was recognised that ligand substitution on the cobalt carbonyl complex might influence the performance of the catalyst. Tertiary alkyl phosphines have a profound influence ... 

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