Metal-carbon bonding in perfluoroethylene and perfluorobenzene transition metal complexes. Some underappreciated π- and σ-acceptor components

Hughes, Russell P.

doi:10.1016/b978-0-12-819874-2.00013-8

Cited by 3 publications

(4 citation statements)

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“…Nickel catalysts 6a, 6b, and 19 were produced by the reaction of ligands 12−14 with Ni(acac) 2 and Ph 3 CB-[C 6 H 3 (CF 3 ) 2 ] 4 . 8 Complexes 6a, 6b, and 19 exist as redpurple, air-stable solids that are soluble in polar solvents such as dichloromethane and insoluble in hexane. They are diamagnetic and thus more conveniently analyzed than the nickel dihalide complexes commonly used as polymerization catalysts.…”

Section: Resultsmentioning

confidence: 99%

“…The solid-state structural differences between fluorinated and nonfluorinated sandwich diimine-nickel and palladium complexes are pronounced, and the catalysts show distinct ethylene polymerization properties as discussed later. The structural features of the fluorinated complexes 16 and 6b, in which the center of the ring is positioned precisely over the metal atom, could conceivably be explained by an electrostatic interaction with the filled dz 2 orbital . For example, C 6 F 6 coordinates water via the electrostatic interaction of oxygen lone pairs with the “π-hole” of the ring .…”

Section: Resultsmentioning

confidence: 99%

“…9a Thus, perfluoroar-enes have a significant Z-type ligand character arising from their ability to act as σ-acceptors. 9b Solid-state stacking of square planar d 8 palladium and platinum complexes with C 6 F 6 , C 5 F 5 N, and C 6 F 5 Cl resulting in "reverse sandwich" structures has been recently reported. 10 The structural features of these complexes are based on noncovalent interactions and in their "π-hole"-Pt(II) and Pd(II) contacts, where metal plays the role of a nucleophile.…”

Section: Structural Analysis Of Complexesmentioning

confidence: 99%

“…Few latetransition-metal olefin polymerization systems tolerate the addition of hydrogen. 8,16 The classical isopropyl-substituted nickel catalyst 2 is rapidly decomposed by hydrogen. 16d We probed whether molecular weight could be controlled with hydrogen, which is routinely used for molecular weight control in early metal systems.…”

Section: Ethylene Polymerization Studies�nickel Catalystsmentioning

confidence: 99%

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Ethylene Polymerizations Catalyzed by Fluorinated “Sandwich” Diimine-Nickel and Palladium Complexes

Medina,

Tran,

Hughes

et al. 2024

J. Am. Chem. Soc.

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Nickel and palladium complexes bearing “sandwich” diimine ligands with perfluorinated aryl caps have been synthesized, characterized, and explored in ethylene polymerization reactions. The X-ray crystallographic analysis of the precatalysts 16 and 6b shows differences from their nonfluorinated analogues 17 and 19, with the perfluorinated aryl caps centered precisely over the nickel and palladium centers, which results in higher buried volumes of the metal centers relative to the nonfluorinated analogues. The sandwich diimine-palladium complexes 5a and 5b containing perfluorinated aryl caps polymerize ethylene in a controlled fashion with activities that are substantially increased compared with their nonfluorinated analogues. Migratory insertion rates in relevant methyl ethylene complexes agree with the activities exhibited in bulk polymerization experiments. DFT studies suggest that facility of ethylene rotation from its preferred orientation perpendicular to the Pd-alkyl bond into a parallel in-plane conformation contributes to the higher polymerization activity for 5b relative to 18a. For these palladium systems, polymer molecular weights can be controlled via hydrogen addition (hydrogenolysis), which is unusual for late-transition-metal-catalyzed olefin polymerizations with no catalyst deactivation occurring. Sandwich diimine-nickel complexes 6a and 6b with perfluorinated aryl caps show ethylene polymerization activities that are about half of those of classical tetraisopropyl-substituted catalyst 2 but again are more active than the analogous nonfluorinated sandwich complexes. Ethylene polymerizations exhibit living behavior, and branched ultrahigh-molecular-weight polyethylenes (UHMWPEs) with very low-molecular-weight distributions (less than 1.1) are obtained. The activated nickel catalysts are stable in the absence of monomer and show good long-term stability at 25 °C.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Structural Analysis Of Complexesmentioning

confidence: 99%

Section: Ethylene Polymerization Studies�nickel Catalystsmentioning

confidence: 99%

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Ethylene Polymerizations Catalyzed by Fluorinated “Sandwich” Diimine-Nickel and Palladium Complexes

Medina,

Tran,

Hughes

et al. 2024

J. Am. Chem. Soc.

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What's Next for First Row Fluorometallacycles?

Baker,

Mangin

2024

Angewandte Chemie

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Hydrocarbon‐derived metallacycles have been identified as key intermediates in a host of catalyzed transformations of unsaturated organic substrates. In contrast, our knowledge of analogous reactivity of fluorometallacycles is underdeveloped and largely confined to first row metals. Our summary of recent advances aims to inform young investigators of the exciting challenges offered by this pursuit.

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