Palladium-Catalyzed Reppe Carbonylation

Abstract

PdX2L2/L/HA (A = weakly coordinating anion, L = phosphine) complexes are active catalysts in the hydroesterification of alkenes, alkynes, and conjugated dienes. Shell, the only major corporate player in the field, recently developed two very active catalyst systems tailored to the hydroesterification of either alkenes or alkynes. The hydroesterification of propyne with their Pd(OAc)2/PN/HA (PN = (2-pyridyl)diphenylphosphine, HA = strong acid with weakly coordinating anion, like methanesulfonic acid) catalyst has been declared commercially ready. However, despite the significant progress in the activity of Pd-hydroesterification catalysts, further improvements are warranted. Thus, for example, activity maintenance still seems to be an issue. Homogeneous Pd catalysts are prone to a number of deactivation reactions. Activity and stability promoters are often corrosive and add to the complexity of the system, making it less attractive. Nonetheless, the versatility of the process and its tolerance toward the functional groups of substrates should appeal especially to the makers of specialty products. Although hydroesterification yields esters from alkenes, alkynes, and dienes in fewer steps than hydroformylation does, the latter has some advantages at the current state of the art. (1) Hydroformylation catalysts, particularly some recently published phosphine-modified Rh systems, can achieve very high regioselectivity for the linear product that hydroesterification catalysts cannot match yet. By analogy with hydroformylation, bulkier ligands ought to be tested in hydroesterification to increase normal-ester selectivity. (2) Hydroformylation is proven, commercial. Hydroesterification can only replace it if it can provide significant economic incentives. Similar or just marginally better performance could not justify the cost of development of a new technology. (3) Hydroesterification requires pure CO while hydroformylation uses syngas, a mixture of CO and H2. The latter is typically more available and less expensive (for industrial applications CO is most often separated from syngas). (4) The acid component of the hydroesterification catalyst makes the process corrosive. It would be desirable to develop new hydroesterification catalysts that do not require acid stabilizer/activity booster. Clearly, any new hydroesterification technology will directly compete with the hydroformylation route. This is especially true for olefin feeds, since both processes add one CO to the olefin, yielding oxygenates that can be converted into identical products. For some niche applications, like the production of MMA from propyne, hydroesterification seems to have an advantage as compared to hydroformylation due to the high activity and selectivity of the Pd(OAc)2/(2-pyridyl)diphenylphosphine catalyst. Since hydroesterification is an emerging technology, it is reasonable to assume that the potential for improvement is greater than in the mature hydroformylation. It is therefore possible that hydroesterification will become competitive in ...

Synthesis, characterization and catalytic activity in the carbonylation of ethene of cis-[Pd(H2O)2(PPh3)2]X2·nH2O (X=p-CH3C6H4SO3, n=2; X=CH3SO3, n=0). X-ray structure of cis-Pd(H2O)2(PPh3)2](p-CH3C6H4SO3)2·2H2O and of cis-[Pd(H2O)2(PPh3)2](CH3SO3)2·2CH2Cl2

“…In the present study, the tetrahedral distortion is limited to 6.5°, a value similar to that of 6.1°found by Mak and co-workers [35] in cis-[(Ph 2 Ppym) 2 PdCl 2 ] AE 1/ 2CH 2 Cl 2 and smaller than those found either by Jensen and co-workers [36] in cis-PdCl 2 [P(CH 3 ) 3 ] 2 and Romerosa et al [37] in [cis-Pd(8-BzTT) 2 (PPh 3 ) 2 ] (8.9°and 13.2°, respectively). The little steric demand of the two coordinated water molecules in the present complex, if compared to the bulk of other ligands [35][36][37], also contributes to keep the tetrahedral distortion to a minimum and help in stabilizing the cis geometry.…”

“…Pd(II)-phosphine complexes in which the cationic charge is balanced by weakly coordinating anions readily displaceable by the reagents are efficient catalysts for the carbonylation of olefins [1,2]. A wide spectrum of products can be obtained.…”

“…The first highly efficient catalyst system that produced a polyketone was prepared by Drent et al [4,5], of Shell Co., from equimolar amount of [Pd(AcO) 2 ] and 1,3-bis(diphenylphosphine)propane together with two equivalents of a Bronsted acid, such as p-CH 3 C 6 H 4 -SO 3 H or HBF 4 , which displaces the acetate anion with formation of a cationic complex having coordination sites readily available to the monomers. In contrast, the catalyst prepared from [Pd(AcO) 2 ], an excess of PPh 3 and of a Bronsted acid, produced selectively propanoate [5]. It was proposed that the striking difference in selectivity is related to the coordination geometry of the ligands.…”

“…In polar solvents, like methanol, the in situ generated species from [Pd(AcO) 2 [10]. Up to now scarce attention has been paid to the geometry of the species generated from the precursor, although it may be of paramount importance on influencing the catalytic activity and selectivity.…”

Ruthenium-catalysed alkoxycarbonylation of alkenes with carbon dioxide

“…Apart from polymerization and oxidation 1,2 , carbonylation reactions using carbon monoxide represent a major technology for the production of value-added bulk and fine chemicals from olefins 3 . In addition to industrial hydroformylation processes that provide aldehydes [4][5][6][7] , the alkoxycarbonylation of alkenes constitutes a straightforward approach to carboxylic acid esters 8 . On an industrial scale, the resulting aliphatic esters are mainly used for the production of detergents and polymer-building blocks.…”