Phase engineering of nanomaterials

The P,O‐chelated shell higher olefin process (SHOP) type nickel complexes are practical homogeneous catalysts for the industrial preparation of linear low‐carbon α‐olefins from ethylene. We describes that a facile synthetic route enables the modulation of steric hindrance and electronic nature of SHOP‐type nickel complexes. A series of sterically bulky SHOP‐type nickel complexes with variable electronic nature, {[4‐R‐C6H4C(O) = C‐PArPh]NiPh (PPh3); Ar = 2‐[2′,6′‐(OMe)2C6H3]C6H4; R = H (Ni1); R = OMe (Ni2); R = CF3 (Ni3)}, were prepared and used as single component catalysts toward ethylene polymerization without using any phosphine scavenger. These nickel catalysts exhibit high thermal stability during ethylene polymerization and result in highly crystalline linear α‐olefinic solid polymer. The catalytic performance of the SHOP‐type nickel complexes was significantly improved by introducing a bulky ortho‐biphenyl group on the phosphorous atom or an electron‐withdrawing trifluoromethyl on the backbone of the ligand, indicating steric and electronic effects play critical roles in SHOP‐type nickel complexes catalyzed ethylene polymerization.

Section: Catalytic Evaluation For Ethylene Polymerizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Facile synthesis of sterically demanding SHOP‐type nickel catalysts for ethylene polymerization

Peng

Pang

et al. 2019

“…Late-transition metal complexes are one of the most extensively studied systems in the field of olefin polymerization and oligomerization because of their low oxophilicity. [1][2][3][4][5] Ni-and Pd-based complexes exhibited high catalytic activity in oligo-/polymerization, [6][7][8][9][10][11][12][13][14] and produced ethylene oligomers or low molecular weight branched polyethylenes. [15][16][17][18][19][20][21][22][23][24] These catalysts were generally ligated by α-diimine, [14,[25][26][27][28][29][30][31] iminopyridyl, [32][33][34] iminepyridazine, [35] iminopyrrolyl, [36] salicylaldimine, [37,38] and many others.…”

Section: Introductionmentioning

confidence: 99%

Bulky iminophosphine‐based nickel and palladium catalysts bearing 2,6‐dibenzhydryl groups for ethylene oligo‐/polymerization

Wang

et al. 2020

A series of 2,6‐dibenzhydryl substituted bulky Ni and Pd complexes containing P,N‐chelating ligands, {[2,6‐(Ph2CH)2‐4‐R‐C6H2‐N=CH‐C6H4‐2‐PPh2]MX2; MX2 =NiBr2; R = Me (Ni1); R = F (Ni2); MX2 =PdCl2, R = Me (Pd1)}, have been prepared and used as catalyst precursors for ethylene oligo‐/polymerization. Compared to the corresponding 2,6‐diisopropyl Ni catalyst, these bulky Ni precatalysts activated by Et2AlCl exhibited excellent catalytic performance toward ethylene polymerization with activity of up to 1.90 × 105 g PE (mol Ni)−1 h−1, and result in semicrystalline PEs with high molecular weight. The catalytic performance of these bulky P,N‐type complexes was significantly improved by introducing two ortho‐dibenzhydryl on the N‐aryl substituents. However, the formation of C10–C24 oligomers were generated using their palladium catalysts through ethylene oligomerization at high temperatures.

“…However, such developments are often initiated by a trial and error discovery and, spefcifically for cases similar to Brookhart-type catalysts, are followed by systematic optimization of steric and electronic properties of the ligands. [21] The steric tuning of the catalyst is the key parameter that mainly controls the relative rates of chain transfer and chain walking, and subsequent polymer chain length and structure. [3,22] Moreover, such developments have opened a new pathway toward production of linear polyethylenelike structures using liquid olefinic monomers instead of ethylene.…”

Section: Introductionmentioning

confidence: 99%

A mechanistic study on the synthesis of branched functional polyethylene through reactive co‐polymer approach

Jandaghian

Ahmadjo

Mortzavi

et al. 2020

The reactive co‐polymer approach is one of the most promising techniques for the synthesis of functional polyolefins. Following this concept, 1‐hexene and p‐methylstyrene are co‐polymerized in the presence of a generic Brookhart‐type catalyst. The microstructures of the co‐polymers imply the tendency of p‐methylstyrene co‐monomers to place at the end of the structural branches formed by the chain walking reaction. The molar masses of the co‐polymers decrease, not only at higher levels of co‐monomer but surprisingly by decreasing reaction temperature. A mechanism consisting of a highly stable η3 metal–benzyl intermediate, which is quantitatively approved by density functional theory calculations, can delicately justify all the aforementioned observations. A series of the produced co‐polymers is selectively functionalized by maleic anhydride at the benzylic position of p‐methylstyrene, under very mild reaction conditions. Such a reactive intermediate opens the path for the introduction of different types of functionalities in polyolefins. Namely, the grafted co‐polymers were further functionalized by a triazole ring, which provides a transient supramolecular network through intermolecular hydrogen bonding.