1615710-06-9Relevant academic research and scientific papers
Electron-Rich Metal Cations Enable Synthesis of High Molecular Weight, Linear Functional Polyethylenes
Zhang, Wei,Waddell, Peter M.,Tiedemann, Margaret A.,Padilla, Christian E.,Mei, Jiajun,Chen, Liye,Carrow, Brad P.
, p. 8841 - 8850 (2018)
Group 10 metal catalysts have shown much promise for the copolymerization of nonpolar with polar alkenes to directly generate functional materials, but access to high copolymer molecular weights nevertheless remains a key challenge toward practical applications in this field. In the context of identifying new strategies for molecular weight control, we report a series of highly polarized P(V)-P(III) chelating ligands that manifest unique space filling and electrostatic effects within the coordination sphere of single component Pd polymerization catalysts and exert important influences on (co)polymer molecular weights. Single component, cationic phosphonic diamide-phosphine (PDAP) Pd catalysts are competent to generate linear, functional polyethylenes with Mw up to ca. 2 × 105 g mol-1, significantly higher than prototypical catalysts in this field, and with polar content up to ca. 9 mol %. Functional groups are positioned by these catalysts almost exclusively along the main chain, not at chain ends or ends of branches, which mimics the microstructures of commercial linear low-density polyethylenes. Spectroscopic, X-ray crystallographic, and computational data indicate PDAP coordination to Pd manifests cationic yet electron-rich active species, which may correlate to their complementary catalytic properties versus privileged catalysts such as electrophilic α-diimine (Brookhart-type) or neutral phosphine-sulfonato (Drent-type) complexes. Though steric blocking within the catalyst coordination sphere has long been a reliable strategy for catalyst molecular weight control, data from this study suggest electronic control should be considered as a complementary concept less prone to suppression of comonomer enchainment that can occur with highly sterically congested catalysts.
Copolymerization of ethylene and methyl acrylate by cationic palladium catalysts that contain phosphine-diethyl phosphonate ancillary ligands
Contrella, Nathan D.,Sampson, Jessica R.,Jordan, Richard F.
, p. 3546 - 3555 (2014/08/05)
A series of benzo-linked phosphine-diethyl phosphonate (P-PO) and phosphine-bis(diethyl phosphonate) (P-(PO)2) ligands and the corresponding (P-PO)PdMe(2,6-lutidine)+ and (P-(PO) 2)PdMe(2,6-lutidine)+ complexes were synthesized. Cationic (P-PO)PdMe(2,6-lutidine)+ complexes are active for ethylene oligomerization/polymerization, with activities of 2 kg mol-1 h -1 for {κ2-1-PiPr2-2-P(O)(OEt) 2-5-Me-Ph}PdMe(2,6-lutidine)+ (3c), 125 kg mol -1 h-1 for {κ2-1-PPh2-2-P(O) (OEt)2-5-Me-Ph}PdMe(2,6-lutidine)+ (3a), and 1470 kg mol-1 h-1 for {κ2-1-P(2-OMe-Ph) 2-2-P(O)(OEt)2-Ph}PdMe(2,6-lutidine)+ (3b). The polyethylene is highly linear, with over 80% terminal unsaturation and low (230-1890 Da) molecular weight in all cases. 3b copolymerizes ethylene with methyl acrylate, exhibiting highly selective (95%) in-chain (rather than chain-end) acrylate incorporation. The P-(PO)2 catalyst {κ2-1-P(4-tBu-Ph)(2-P(O)(OEt)2-5-Me-Ph)- 2-P(O)(OEt)2-5-Me-Ph}PdMe(2,6-lutidine)+ (3d) is more active for ethylene homopolymerization (2640 kg mol-1 h -1), yielding linear, low-molecular-weight polymer (1280-1430 Da) with predominantly internal olefin placement. In ethylene/methyl acrylate copolymerization, 3d incorporates 2.6 mol % methyl acrylate, 60% of which is in-chain. Both 3b and 3d catalyze ethylene/acrylic acid copolymerization, albeit with low (-1 h-1) activities and acrylic acid incorporation up to 1.1 mol %.
