Effect of a hydride source (water, hydrogen, p -toluenesulfonic acid) on the hydroesterification of ethylene to methyl propionate using a Pd(PPh 3 ) 2 (TsO) 2 (TsO = p -toluenesulfonate anion) catalyst precursor

Abstract

Hydroesterification of ethylene to methyl propionate has been studied using the catalyst precursor Pd(PPh 3 ) 2 (TsO) 2 , which is active in presence of PPh 3 and TsOH (TOF = 5700 h −1 at 120 • C, 40 atm (CO/C 2 H 4 = 1/1), Pd/PPh 3 /TsOH = 1/8/10, [Pd] = 2 × 10 −3 mol l −1 , solvent methanol, H 2 O = 800 ppm). In this paper we study the promoting effect of a hydride source, molecular hydrogen, water and p-toluenesulfonic acid (TsOH) and the inhibiting effect of p-benzoquinone. On the basis of experimental evidences, of the two possible initial steps of the catalytic cycle, the insertion of the olefin into a Pd-H species or into a Pd-OCH 3 species, it is suggested that the first plays a more important role.

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

“…This complex is a key intermediate in the catalytic system based on [Pd(d t bpx)(dba)] [dba = trans,trans-(PhCH᎐ ᎐ CH) 2 CO], 1, and MeSO 3 H used by Lucite International for the highly selective methoxycarbonylation of ethene to give methylpropanoate (MP), 8 a reaction which we have clearly shown to proceed via a hydride catalytic cycle. 7 Circumstantial evidence for the involvement of a Pd-H species in the catalytic methoxycarbonylation of ethene to MP has also been reported by Toniolo et al 9 for a related precursor system containing a monodentate phosphine [Pd(PPh 3 ) 2 (η 1 -OTs) 2 ]/PPh 3 /TsOH (Ts = p-toluenesulfonate), although in this case spectroscopic studies aimed at the identification and structural elucidation of the catalytic intermediates were not carried out. Herein, we report a detailed study on the genesis, stability and reactivity of [Pd(d t bpx)-H(MeOH)] ϩ , 2a, and related complexes.…”

Kinetic models of the cyclohexene hydromethoxycarbonylation catalyzed by the Pd(OAc)2/trans‐2,3‐bis(diphenylphosphinomethyl)norbornane/p‐toluensulfonic acid

“…At the previous stage of kinetic studies, we have studied the effect of the concentration of the catalytic system Pd(OAc) 2 /TBDPN/TsOH components and reagents on the cyclohexene hydromethoxycarbonylation initial rate. The reaction mechanism has been developed based on existing data on the palladium catalytic forms in hydrocarbalkoxylation reactions (Scheme ).…”

New Sustainable Pd(II)/Fe(III) Catalytic System Very Efficient in the Hydromethoxycarbonylation of 1-octene

“…Although the mechanism of hydroalcoxycarbonylation of olefins in the presence of Brönsted acid is widely studied in the literature, we can do some supposition on the role played by FeCl 3 as substituted of the Brönsted acid. Under the reaction conditions, the tosylate ligands in the Pd(II) precursor (weakly coordinating) are readily substituted by the solvent forming a cationic complex in which they are the counter-anions [42] (a in Scheme 2). The active species for the hydromethoxycarbonylation (b and c in Scheme 2), can easily form through reactions 2 and 3.…”

“…The choice of the phosphine ligand plays a fundamental role in determining the catalytic activity of the Pd(II)complex, but the co-presence in solution of an excess of the same ligand and of a Brönsted acid, is almost always needed, in order to obtain the performance required. In fact, the appropriate acidic strength and the coordinative properties of the Brönsted acid (e.g., p-toluenesulfonic acid, TsOH) favor the in situ formation of active Pd-hydride species [26-29, 39, 40], whose decomposition to inactive Pd-metal is efficiently avoided by the presence in solution of the excess of the phosphine ligand (PPh 3 ) [9,[39][40][41][42][43] (see Scheme 1). However, from an industrial point of view, we have also to consider the possible drawbacks and environmental impacts relate to such reaction.…”