Manipulating pre-equilibria in olefin polymerization catalysis: backbone-stiffening converts a living into a highly active salan-type catalyst

Abstract

Stiffening of the catalyst backbone of salan-type catalyst 1 via ring closure yields indanosalan 3 and increases activity and molar mass capability by two orders of magnitude. In propene polymerization,...

CDs “inserted” abundant FeB-based electrode via “local photothermal effect” strategy toward efficient overall seawater splitting

“…A change in the chemical shift is observed, indicating that the doping of CDs could improve the conductivity of the electrode and adjust the microscopic morphology and size to improve the transport of ions. 31,32 The presence of B–O spectra (Fig. 1n) confirms the successful modification of FeB by mild chemical plating, and the doping of B element increases the binding energy of Fe 2p due to the interaction between iron and boron, and this synergistic effect favors HER because the structure of iron oxide/boride composites has a highly selective chimney effect on surface H* adsorption and H 2 desorption, while surface oxidized Fe provides an active site for efficient OER.…”

Trends in Structure and Ethylene Polymerization Reactivity of Transition-Metal Permethylindenyl-phenoxy (PHENI*) Complexes

“…In the 1 H NMR spectrum of 7, the SiCH 3 singlet is at δ 1.04 ppm, and the SiC 6 H 5 resonances are multiplets at δ 7.23−7.32 and 7.78−7.82 ppm. 5), (R)-Z-Med ,n Pr SB( d t Bu 2 ArO,I*)TiCl 2 (6), and (R)-E-Me,Ph SB-( d t Bu 2 ArO,I*)TiCl 2 (7). Hydrogen atoms omitted for clarity; one stereoisomer shown; thermal ellipsoids drawn at 30% [or 15% (6)] probability.…”

“…This leads to increased activities, generally higher molecular weight polymers, and also the ability to incorporate comonomers with high efficiency . The development of new generations of CGCs and related postmetallocene catalystsmany of which incorporate phenoxide ligandsis an area of ongoing intensive research. − …”

“…toluene afforded PHENI* titanium dichloride complexes in isolated recrystallized yields of 20−30%, comparable to the yields reported for PHENICS complexes. In addition to the previously reported complexes 1, 2, and 5, titanium complexes Me,d n Pr SB( d t Bu 2 ArO,I*)TiCl 2 (6) and Me,Ph SB( d t Bu 2 ArO,I*)TiCl 2(7) of the mixed-bridge ligands L4 (Me, n Pr) and L5 (Me,Ph) were prepared and isolated. The comparatively low isolated d t Bu 2 ArO,I*)HfCl 2…”

Triptycene as a scaffold in metallocene catalyzed olefin polymerization

“…Catalysis of olefin polymerization is all about control: control of stereochemistry, [1][2][3][4][5][6][7] of regiochemistry (1,2 vs. 2,1 insertion), [8][9][10][11] of molecular weight (insertion vs. β-H transfer and hydrogenolysis), 2,[12][13][14][15] of chemoselectivity (ethene vs. propene vs. α-olefins), [16][17][18][19][20] of catalyst stability ( propagation vs. deactivation), [21][22][23][24] and catalyst activity. [25][26][27][28] For typical catalyst classes the main factor is sterics. 29,30 Stereoselectivity is completely determined by steric interactions between ligand, growing chain and incoming monomer.…”