Acrylate formation from CO₂ and ethylene: catalysis with palladium and mechanistic insight

Abstract

We report the first catalyst based on palladium for the reaction of CO2, alkene and a base to form sodium acrylate and derivatives. A mechanism similar to a previously reported Ni(0)-catalyst is proposed based on stoichiometric in situ NMR experiments, isolated intermediates and a parent palladalactone. Our palladium catalyst was applied to the coupling of CO2 with conjugated alkenes.

Palladium‐ and Nickel‐Catalyzed Synthesis of Sodium Acrylate from Ethylene, CO2, and Phenolate Bases: Optimization of the Catalytic System for a Potential Process

“…Without Zn, the Pd II precursors were less active compared with [PdCl 2 (COD)] ( Table 2, entries 8-10) as expected according to previous investigations, Ni 0 and Pd 0 complexes are active species in the catalytic cycle, [9] which makes them very sensitive towards traces of oxygen. Assuming that the role of Zn is to activate the precatalyst generating the active Pd 0 species, we tested further Pd II precursors.…”

“…As shown in previous work on nickel [6,8] and palladium catalysts [9] reported from our laboratory and by Vogt et al, [7] the direct synthesis of acrylic acid from CO 2 and ethylene is thermodynamically not feasible. [6] However, the carboxylation of ethylene is made exergonic by addition of a base to generate the corresponding sodium acrylate (Scheme 2).…”

“…The sodium phenolate in the organic mixture can then be regenerated by addition of NaOH under removal of water after separation of the product. [9] According to the preliminary screening, di-alkyl substitution in the ortho-positions of the phenolate seems to strongly effect the activity. [6,10] In this context, it was first necessary to identify whether any of the previously reported Ni-and Pd-catalysts are compatible with di-ortho-substituted sodium phenolates as the base (Table 1).…”

The coupling of carbon dioxide with ethene to produce acrylic acid sodium salt in one pot by using Ni(II) and Pd(II)-phosphine complexes as precatalysts

“…Nevertheless, from an industrial point of view, it is still considered as a viable alternative option to some traditional processes in particular when the target products are value-added, economical and in demand [9][10][11][12][13][14][15]. As a matter of fact, the industrial utilization of CO 2 is presently limited to the production of bulk chemicals like salicylic acid, urea, cyclic carbonates and polypropylene carbonate [7][8][9][10]15], even if one of the most interesting challenge for the industry is represented by the CO 2 coupling with olefins to produce acrylate [16][17][18][19][20][21][22][23][24][25][26]. This process would be sustainable and economical, as applications of acrylates are ubiquitous, particularly in the field of coatings, adhesives, construction chemicals, hygiene products and paints.…”

“…The most used route to form such species is the in situ synthesis from Ni(0) complexes, such as Ni(COD) 2 , Ni(PPh 3 ) 4 , etc., and the suitable ligands. As the Ni(0) sources would be difficult to handle and manipulate because of their high air sensitivity and thermal instability, in some papers the more stable Ni(II) complexes are used as pre-catalysts, which are then reduced in situ to zerovalent nickel usually by treatment with external reductants, for instance by addition of zinc dust [13][14][15][16][17]47]. Also the Pd(0) complexes catalyze the title reaction but they activity is usually lower than by using Ni(0) precursors.…”