Recent decades have witnessed intense research efforts aimed at developing new homogeneous olefin polymerization catalysts, with a primary focus on metal-Cl or metal-hydrocarbyl precursors. Curiously, metal-NR 2 precursors have received far less attention. In this contribution, the Zr-amido complex FI 2 ZrX 2 (FI = 2,4-di-tert-butyl-6-((isobutylimino)methyl)phenolate, X = NMe 2 ) is found to exhibit high ethylene polymerization activity and relatively high 1-octene coenchainment selectivity (up to 7.2 mol%) after sequential activation with trimethylaluminum, then Ph 3 C + B(C 6 F 5 ) 4− . In sharp contrast, catalysts with traditional hydrocarbyl ligands such as benzyl and methyl give low 1-octene incorporation (0-1.0 mol%). This unexpected selectivity persists under scaled/industrial operating conditions and was previously inaccessible with traditional metal-Cl or -hydrocarbyl precursors. NMR, X-ray diffraction, and catalytic control experiments indicate that in this case an FI ligand is abstracted from FI 2 Zr(NMe 2 ) 2 by trimethylaluminum in the activation process to yield a catalytically active cationic mono-FIZr species. Heretofore this process was believed to serve only as a major catalyst deactivation pathway to be avoided. This work demonstrates the importance of investigating diverse precatalyst monodentate σ-ligands in developing new catalyst systems, especially for group 4 olefin polymerization catalysts.

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Binuclear dianionic cocatalysts can bring cationic active metal centers into close proximity to study center–center enchainment cooperativity effects in olefin polymerization catalysis. The previously reported binuclear diborate cocatalyst, (Ph3C+)2[1,4-(C6F5)3BC6F4B­(C6F5)3]2– (B 2,H ), is poorly soluble in alkane and aromatic solvents and requires undesirable haloaromatic additives to fully solubilize it for efficient olefin polymerizations. Here, two binuclear diborate-based cocatalysts, (Ar3C+)2[1,4-(C6F5)3BC6F4B­(C6F5)3]2– (B 2,t‑Bu ; Ar = 4-t-Bu-C6H4-; B 2,n‑octyl ; Ar = 4-n-octyl-C6H4-), are synthesized and characterized by multinuclear NMR spectroscopy, density functional theory computation, and by single-crystal diffraction for B 2,t‑Bu . B 2,n‑octyl exhibits good solubility in low-polarity solvents such as toluene and methylcyclohexane (MeCy), enabling the study of (μ-CH2CH2-3,3′)­{(η5-indenyl)­[1-Me2Si­( t BuN)]­(ZrMe+)2 [EBICGC­(ZrMe+)2]-catalyzed ethylene homo- and co-polymerizations in solvent systems of decreasing polarity (toluene/difluorobenzene → toluene → MeCy). Product M ws are bimodal and sensitive to the above solvent progression, with the high-M w fraction (wt %) increasing from 41 → 92 → 100%, respectively, for ethylene homopolymerization, and from 15 → 53 → 93%, respectively, for ethylene + 1-hexene copolymerization. Under scaled/industrial high temperature, higher pressure operating conditions, the same soluble binuclear diborate is an active olefin copolymerization cocatalyst, giving high polymer M ws and similar dispersity, D̵.

Although interfacial hydrogen has long been accepted as the species responsible for H2 detection in metal-insulator-semiconductor (MIS) sensors, direct observation of this species has been elusive. In this work, the use of neutron reflectivity (NR) to quantify the hydrogen concentration in regions of an MIS device is reported. The presence of multiple states at both the metal-insulator interface and within the insulator that may contribute to the hydrogen response is suggested by the scattering length density profiles obtained from NR. This technique provides a great promise for direct study of the detection mechanisms for MIS sensors.