Cyclometalated group 4 complexes supported by tridentate pyridine-2-phenolate-6-(σ-aryl) ligands: Catalysts for ethylene polymerization and comparisons with fluorinated analogues

Weak Attractive Ligand–Polymer and Related Interactions in Catalysis and Reactivity: Impact, Applications, and Modeling

“…We recently designed and synthesized a series of Group 4 complexes supported by [O,N,C] ligands (important examples are shown in Scheme ) 48. 49…”

Scalar Coupling Across [CH⋅⋅⋅FC] Interactions in (σ‐Aryl)‐Chelating Post‐Metallocenes

“…Researchers at Symyx and Dow have developed a class of pyridylamido [N,N,C]-Hf isotactic propylene polymerization catalysts (which are amide congeners of the [O,N,C] system) through the use of high-throughput screening, and described their application in tandem with Zr bis(phenoxyimine) catalysts for the commercial-scale production of multiblock polyolefin materials by a novel chain-shuttling polymerization process. [29] In contrast, our olefin polymerization studies on Ti-[O,N,C] catalysts often revealed multi-site behavior, [24,30] which was ascribed to a strained TiÀCA C H T U N G T R E N N U N G (aryl) linkage and subsequent olefin insertion therein to afford additional, modified catalytic entities. [31] Detailed studies on the [N,N,C]-Hf system (C = 1-naphthyl) have similarly described favorable olefin insertion into the Hf À CA C H T U N G T R E N N U N G (aryl) bond, which is weakened as a steric consequence of the naphthyl moiety, to generate "monomer-inserted" catalysts.…”

Olefin Polymerization Reactivity of Group 4 Post‐Metallocene Catalysts Bearing a Four‐Membered C(sp3)‐Donor Chelate Ring

“…While studies on 2 and 5 indicated the absence of CÀ H···FÀ C interactions, the [ 1 H, 19 F]-HMQC spectrum for 3 ( Figure S4) reveal a strong crosspeak between the o-CF 3 group and the methine (H 12 ) proton, and a noticeably weaker crosspeak with one of the four methylene protons, while the selective [ 1 H, 19 F]-HMBC (J) spectrum ( Figure S5) demonstrates scalar coupling for these interactions. [6] Considering the highly sensitive nature of these NMR pulse sequences, and the absence of discernible 1h J H,F or 2h J C,F coupling in the 1 H (the H 12 resonance is slightly broad but 19 F-coupling is unresolved) and 13 C NMR spectra, we conclude that (1) the intraligand C-(methine)À H···FÀ C interaction is weak but could persist during polymerization in the absence of competing interactions, and (2) the apparent C(methylene)-H···FÀ C interaction is likely to be too weak (particularly for a benzyl group with greater flexibility within the cationic species) to impact appreciably with regards to WALPI-type catalysis (see below).…”

“…[1] With regards to anionic C(sp 2 )-donor ligands, interest in Group 4 complexes supported by chelating σ-aryl auxiliaries has flourished, [2] particularly for the 2-aryloxoand 2-arylamido-6-(σ-aryl)-pyridine ([O,N,C] and [N,N,C] respectively) ligand systems independently reported by our group [3] and researchers at Symyx and Dow. [4] We have described the observation of intramolecular CÀ H···FÀ C interactions in fluorinated [O,N,C] [5] and related [O,C,N] [6] Group 4 precatalysts using NMR spectroscopic and neutron diffraction studies. These complexes constitute synthetic models of 'weak attractive ligand-polymer interactions' (WALPI), a new strategy in olefin polymerization reactions that offers the capability to manipulate the reactivity of the polymer chain during catalysis.…”

“…Perspective views of 1-Zr (top) and 7-Zr (bottom; 30 % probability ellipsoids and hydrogen atoms omitted for clarity). Selected bond lengths (Å) and angles (deg) for 1-Zr: Zr1-N1 2.220(1), Zr1-C12 2.399(2), Zr1-C27 2.278(2), Zr1-C34 2.295(1), C11-C12 1.475(2), C12-C13 1.480(3), O1-Zr1-C12 137.07(5), C11-C12-C13 120.60(1); for 7-Zr: Zr1-N1 2.249(4), Zr1-N2 2.262(5), Zr1-C26 2.273(7), Zr1-C33 2.308(6), C11-C12 1.415(8), C12-C13 1.391(8), O1-Zr1-N2 163.80(2), C13-C12-C11 131.10(6).…”