Synthesis and reactivity of palladium hydrido-solvento complexes, including a key intermediate in the catalytic methoxycarbonylation of ethene to methyl propanoate

Abstract

The sequence of reaction steps and the role of each reactant, required for the transformation of the Pd( 0] ϩ , 2a, the active Pd()-hydride catalyst for the methoxycarbonylation of ethene to methylpropanoate, have been delineated using a combination of spectroscopic and crystallographic methods. The preparation and characterisation of a variety of related complexes are described including some unusual examples involving bidentate sulfonate complexes and mono-cationic and neutral palladium hydride complexes. X-Ray crystal structures have been determined for [Pd(2-(CH 2 PCy 2 ) 2 C 6 H 4 ], 7, and [Pd(d t bpx)(η 2 -MeSO 3 )] ϩ , 9b.

Following palladium catalyzed methoxycarbonylation by hyperpolarized NMR spectroscopy: a parahydrogen based investigation

“…We note that the dihydride [Pd(H) 2 (bcope)] would be PHIP active because of the second order nature of its hydride ligands. 72 Hence, as it is not detected, we can conclude that it is either too reactive to be seen, which is unlikely given the previous observation of ( t BuCOPE)Pd(H) 2 or that the contribution of a dihydride based reaction pathway is minimal in agreement with earlier literature predictions. 57,73 We conclude therefore that PHIP reflects an ideal platform from which to study this methoxycarbonylation reaction and thereby establish its potential to follow a wider range of catalytic processes than was previously thought possible.…”

“…1 High molecular weight thermoplastics, and the production of methylpropanoate 2 , reflect other high value products that are formed on an industrial scale via this reaction, which is most clearly illustrated by Lucite's Alpha process, one of the many successes of palladium catalysis. In addition, the alkoxycarbonylatyion of 1-alkynes finds a further role in the formation of unsaturated carboxylic acids that feature as building blocks in a range of situations.…”

“…In addition, the alkoxycarbonylatyion of 1-alkynes finds a further role in the formation of unsaturated carboxylic acids that feature as building blocks in a range of situations. 3,4 Consequently, these developments illustrate just how critical early studies on the mechanism of the methoxycarbonylation of alkenes, 2,5 and more generally the palladium catalysed hydroformylation of alkenes 6,7 were for the development of an array of new clean technologies. 3 For a number of years, the parahydrogen (p-H 2 ) 8 induced polarization (PHIP) 9, 10 effect has been used to yield mechanistic insight into a range of catalytic hydrogenation and hydroformlyation reactions besides monitoring the formation of metal hydride based products.…”

“…We have selected the palladium catalysed methoxy-carbonylation of an alkyne for this purpose, a reaction that has been widely studied, and hence provides a good background from which to work. 2,[40][41][42][43][44] Leeuwen has completed a range of studies on this reaction as a function of phosphine 40,46 with Claver completing related studies on vinyl arenes. 43 The alkoxycarbonylation of alkynes by palladium has also been examined.…”

Development of a kinetic model of ethylene methoxycarbonylation with homogeneous Pd catalyst using a capillary microreactor

“…Clegg et al [14] and Eastham et al [15] showed that the palladium catalysed methoxycarbonylation of ethylene follows the hydride cycle (A) which represents the predominant route to MeP formation. The Pd-hydride reacts with ethylene to form the…”