On the Mechanism of the Hydroxycarbonylation of Styrene with Palladium Systems

Abstract

We present a review concerning the mechanism involved in the hydroxycarbonylation of styrene. We discuss the intermediates proposed in the literature, the effect of the acidic medium, the reactivity and kinetics, as well as the results of theoretical calculations on hydroxycarbonylation and related reactions. We have performed an in situ high-pressure NMR [a] Inmaculada del Río (left) received her Ph.D. in 2000 from the University Rovira i Virgili working on mechanistic aspects of hydroformylation and hydroxycarbonylation reactions. Carmen Claver (right) is Professor of Inorganic Chemistry at the University Rovira i Virgili in Tarragona (Spain), a position she has held since 1991. She received her Ph.D. in 1978 from the University of Zaragoza (Spain) working in the field of organometallic chemistry with Prof. Luis A. Oro. Her present research is focused on fundamental aspects of homogeneous catalysis with transition metals, especially in asymmetric catalysis. Piet W. N. M. van Leeuwen is Professor of Homogeneous Catalysis at the University of Amsterdam, a position he has held since 1989. He has spent much of his career at Shell Research in Amsterdam working in the area of homogeneous catalysis and organometallic chemistry. His present research is aimed at the development of novel transition metal homogeneous catalysts, using the full range of available tools and techniques.MICROREVIEWS: This feature introduces the readers to the authors' research through a concise overview of the selected topic. Reference to important work from others in the field is included.2719 study to obtain more insight into the mechanisms that control the regioselectivity and have assessed how this is affected by the phosphorus ligand and the catalyst precursor. We observed palladium hydride and palladium acyl species and we suggest a catalytic cycle involving palladium hydride, palladium alkyl, and palladium acyl intermediates.

Methoxycarbonylation of olefins catalyzed by palladium(II) complexes containing naphthyl(diphenyl)phosphine ligands

“…This mechanism suggests that Pd‐hydride and Pd‐OMe are the active species in the catalytic reaction. On the other hand the Claver group proposed a mechanism for hydroxycarbonylation of styrene using palladium complexes. They found that palladium hydride and palladium acyl species were present, which suggests a catalytic cycle involving palladium hydride, palladium alkyl and palladium acyl intermediates .…”

Asymmetric Carbonylations

“…The production of the Pd -H species from complexes formed in Cycle B was also demonstrated to occur through the β -elimination of an unsaturated ester after alkene insertion. When the substrate is a vinylarene, the branched alkyl intermediate can be stabilized through the formation of π -benzylic species, with the two complexes in equilibrium [44] . The coexistence of these two cycles was suggested to be the origin of the regioselectivity of these reactions, based on steric factors that would favor the linear insertion of styrene into a Pd -hydride bond, whereas the branched insertion of styrene would be favored into a Pd -alkoxycarbonyl bond [45] .…”

“…The use of bidentate ligands generally leads to a greater amount of linear products, whereas catalytic systems bearing monodentate ligands usually favor the formation of the branched products [46] . This difference in regioselectivity was suggested to be due to the ability of monodentate ligands to coordinate to the palladium center in a cis or a trans manner [44] . However, the study of the alcoholysis step, performed varying the bite angle of diphosphines, indicated that cis coordination of the phosphine ligands is required for this step to be effi cient [47] .…”

“…Recent advances have been reported on the methanolysis step using DFT calculation methods [51] . However, the origin of the regioselectivity of these reactions is still to be established [44] .…”

Methoxycarbonylation of Styrene by Palladium(ii) Complex Containing the Diphenylphosphinocyrhetrene Ligand

“…Catalysts containing bidentate diphosphine ligands have been more frequently used for this reaction, but they have the disadvantage to produce branched product in low regio-and enantioselectivity, although a few successful examples have been reported recently. [3][4][5][6][7] Several chelating diphosphines have been extensively studied, particularly interesting are those containing metallocenic fragments, for instance, palladium(II) complexes with 1,1-bis(diphenylphosphino)ferrocene (dppf), 1,1-bis(diphenylphosphino) octamethylferrocene (dppomf), 1,1-bis(diphenyl-phosphino)ruthenocene (dppr), and bis(diphenylphosphino)osmocene (dppo) have proven to catalyze the methoxycarbonylation of ethylene and styrene, showing high selectivity to the linear ester. [8][9][10][11][12][13] Gusev et.…”