925941-62-4Relevant academic research and scientific papers
Formation of linear copolymers of ethylene and acrylonitrile catalyzed by phosphine sulfonate palladium complexes
Kochi, Takuya,Noda, Shusuke,Yoshimura, Kenji,Nozaki, Kyoko
, p. 8948 - 8949 (2007)
Linear copolymers of ethylene and acrylonitrile were prepared using palladium complexes bearing phosphine-sulfonate bidentate ligands. Acrylonitrile units located in the linear polyethylene backbones were detected for the first time by 13C NMR spectroscopy. Catalyst systems employing isolated palladium complexes such as 3 showed much higher activity for the copolymerization than the in situ generation procedures, and molecular weight of the copolymers and acrylonitrile incorporation were dependent on the palladium complexes. Obtained linear copolymers of ethylene and acrylonitrile melt at higher temperature than branched copolymers. Copyright
Limits of activity: Weakly coordinating ligands in arylphosphinesulfonato palladium(II) polymerization catalysts
Neuwald, Boris,Oelscher, Franz,Goettker-Schnetmann, Inigo,Mecking, Stefan
, p. 3128 - 3137 (2012/06/04)
The coordination strength of various phosphine oxides OPR3 toward the olefin polymerization catalyst (PλO)PdMe (P λO = κ2-P,O-Ar2PC 6H4SO2O with Ar = 2-MeOC6H 4) as compared to that of dmso has been determined. Equilibrium constants KL for the reaction 1-dmso + L ? 1-L + dmso range from 3.5 for electron-rich OPBu3 to 10-3 for electron-poor OP(p-CF3C6H4)3. Complexes derived from more strongly coordinating phosphine oxides, i.e. [(PλO) PdMe(L)] (1-L; L = OPBu3, OPOct3, OPPh3) have been isolated and fully characterized. Additionally, 1-OPBu3 and 1-OPPh3 were analyzed by X-ray diffraction analyses. Complexes derived from weakly coordinating phosphine oxides have eluded isolation due to loss of phosphine oxide and formation of barely soluble multinuclear palladium complexes 1n by bridging coordination of the sulfonate group to various Pd centers. Hence, the (PλO)PdMe fragment 1 exhibits an intrinsic limitation with respect to coordination of weak donors. Species 1 generated in situ in the absence of additional ligand (L) has been identified in homo- and copolymerization experiments as well as NMR insertion studies as the most active possible catalyst. Since 1 is generated from the easily available precursor [{(1-Cl)-ν-Na}2)], these findings give rapid access to highly active (PλO)PdMe catalysts.
Mechanistic insights on acrylate insertion polymerization
Guironnet, Damien,Caporaso, Lucia,Neuwald, Boris,G?ttker-Schnetmann, Inigo,Cavallo, Luigi,Mecking, Stefan
, p. 4418 - 4426 (2010/06/13)
Complexes [{(PΛO)PdMe]n] (1n; PΛO = K2-P, O-Ar2PC6H4SO2O with Ar = 2-MeOC6H4) are a single-component precursor of the (PΛO)PdMe fragment devoid of additional coordinating ligands, which also promotes the catalytic oligomerization of acrylates. Exposure of 1n to methyl acrylate afforded the two diastereomeric chelate complexes [(PΛO)Pd{k2-C,O-CH(C(O)OMe)CH2CH(C(O)OMe)CH 2CH3}] (3-meso and 3-rac) resulting from two consecutive 2,1-insertions of methyl acrylate into the Pd-Me bond with the same or opposite stereochemistry, respectively, in a 3:2 ratio as demonstrated by comprehensive NMR spectroscopic studies and single crystal X-ray diffraction. These six-membered chelate complexes are direct key models for intermediates of acrylate insertion polymerization, and also ethylene-acrylate copolymerization to high acrylate content copolymers. Studies of the binding of various substrates (pyridine, dmso, ethylene and methyl acrylate) to 3-meso and 3-rac show that hindered displacement of the chelating carbonyl moiety by π-coordination of incoming monomer significantly retards, but does not prohibit, polymerization. For 3-meso,3-rac + C2H4 ? 3-meso-C2H4 3-rac-C2H4 an equilibrium constant K(353 K) ≈ 2 × 10-3 L mol-1 was estimated. Reaction of 3-meso, 3-rac with methyl acrylate afforded higher insertion products [(PΛO)Pd(C4H6O2).,Me] (n = 3, 4) as observed by electrospray ionization mass spectrometry (ESI-MS). Theoretical studies by DFT methods of consecutive acrylate insertion provide relative energies of intermediates and transition states, which are consistent with the aforementioned experimental observations, and give detailed insights to the pathways of multiple consecutive acrylate insertions. Acrylate insertion into 3-meso,3-rac is associated with an overall energy barrier of ca. 100 kJ mol-1
