Palladium Aryl Sulfonate Phosphine Catalysts for the Copolymerization of Acrylates with Ethene

Abstract

The reaction of 2‐[bis(2‐methoxy‐phenyl)phosphanyl]‐4‐methyl‐benzenesulfonic acid (a) and 2‐[bis(2′,6′‐dimethoxybiphenyl‐2‐yl)phosphanyl]benzenesulfonic acid (b) with dimethyl(N,N,N′,N′‐tetramethylethylenediamine)‐palladium(II) (PdMe2(TMEDA)) leads to the formation of TMEDA bridged palladium based polymerization catalysts (1a and 1b). Upon reaction with pyridine, two mononuclear catalysts are formed (2a and 2b). These catalysts are able to homopolymerize ethylene and also copolymerize ethylene with acrylates or with norbornenes. With ligand b, high molecular weight polymers are formed in high yields, but higher comonomer incorporations are obtained with ligand a.magnified image

Investigation of Steric and Electronic Factors of (Arylsulfonyl)phosphane‐Palladium Catalysts in Ethene Polymerization

“…The catalyst synthesis proceeds smoothly following the procedure highlighted in the literature. [12] The yields are in the following order: 1Pd ≈ 2Pd Ͼ 3Pd Ͼ 4Pd Ͼ 5Pd, which does not follow the expected basicity of those ligands, thereby indicating that steric factors are the dominant influence in determining the reactivity of these sulfonated phosphanes towards Pd centers. For the sake of clarity, the term catalyst will be used for compounds 1Pd to 5Pd, although they are only catalysts once pyridine is replaced by ethene (initiating efficiency may be vastly different for each of them).…”

“…gand were then disclosed by Hearley et al, [6] Goodall et al, [7,8] Kochi et al, [9,10] Liu et al, [11] Skupov et al, [12] Luo et al, [13] Vela et al, [14] and most recently Guironnet et al [15] Among those reports, acrylate copolymerization with ethene was mentioned by Goodall, [7,8] Skupov, [12] and Guironnet. [15] These studies employ the catalyst [(oAr 2 PC 6 H 4 SO 3 )PdMe(L)] with Ar = o-OMePh, which corresponds to the ligand originally presented by Drent.…”

“…However, at this time, little is known on the influence of the arylphosphane sulfonate structure. We recently reported that introduction of the bulky and electron-rich aryl groups (Ar = -{o-[2Ј,6Ј-(OMe) 2 C 6 H 3 ]-C 6 H 4 }) resulted in a very active catalyst that affords polyethylene of high molecular weight [12] but with a modest propensity to incorporate any other monomer than ethene. We infer that this behavior stems from the steric hindrance, which precludes the facile coordination of any olefin larger than ethene.…”

“…[15] These studies employ the catalyst [(oAr 2 PC 6 H 4 SO 3 )PdMe(L)] with Ar = o-OMePh, which corresponds to the ligand originally presented by Drent. [5] The role of the ancillary ligand L (L = pyridine, [12,16] lutidine, [17] DMSO, [15] or allyl group [11] ) on the catalytic activity has been studied in detail. However, at this time, little is known on the influence of the arylphosphane sulfonate structure.…”

Coordination Copolymerization of Polar Vinyl Monomers H2CCHX

“…In a typical copolymerization experiment with this catalyst, an ethylene-MA copolymer with 6 mol % MA incorporation and M n = 10 4 g mol À1 is formed with an average catalyst activity of 7 10 2 TO h À1 . [27] A comparison of polymerizations with 7 and cationic Pd II dimine catalysts (N^N)PdR + is instructive: 1) linear (semicrystalline) polymers are obtained with 7, while highly branched amorphous polymers are obtained with (N^N)PdR + , likely owing to slow b-hydride elimination relative to chain growth with 7. 2) k-X coordination in general is less an issue with the less electrophilic 7.…”