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Unusual Reactivity of N,N,N ,N -Tetramethylethylenediamine-Coordinated Neutral Ni(II) Polymerization Catalysts

Unusual Reactivity of N,N,N ,N -Tetramethylethylenediamine-Coordinated Neutral Ni(II) Polymerization Catalysts

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BERKEFELD, Andreas, Heiko M. MÖLLER, Stefan MECKING, 2009. Unusual Reactivity of N,N,N ,N -Tetramethylethylenediamine-Coordinated Neutral Ni(II) Polymerization Catalysts. In: Organometallics. 28(14), pp. 4048-4055. ISSN 0276-7333

@article{Berkefeld2009Unusu-1030, title={Unusual Reactivity of N,N,N ,N -Tetramethylethylenediamine-Coordinated Neutral Ni(II) Polymerization Catalysts}, year={2009}, doi={10.1021/om900198c}, number={14}, volume={28}, issn={0276-7333}, journal={Organometallics}, pages={4048--4055}, author={Berkefeld, Andreas and Möller, Heiko M. and Mecking, Stefan} }

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:bibo="http://purl.org/ontology/bibo/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:xsd="http://www.w3.org/2001/XMLSchema#" > <rdf:Description rdf:about="https://kops.uni-konstanz.de/rdf/resource/123456789/1030"> <bibo:uri rdf:resource="http://kops.uni-konstanz.de/handle/123456789/1030"/> <dc:language>eng</dc:language> <dc:date rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2011-03-22T17:54:51Z</dc:date> <dc:creator>Berkefeld, Andreas</dc:creator> <dcterms:title>Unusual Reactivity of N,N,N ,N -Tetramethylethylenediamine-Coordinated Neutral Ni(II) Polymerization Catalysts</dcterms:title> <dc:creator>Möller, Heiko M.</dc:creator> <dc:rights>deposit-license</dc:rights> <dc:contributor>Möller, Heiko M.</dc:contributor> <dc:contributor>Berkefeld, Andreas</dc:contributor> <dc:creator>Mecking, Stefan</dc:creator> <dcterms:bibliographicCitation>Organometallics ; 28 (2009), 14. - S. 4048-4055</dcterms:bibliographicCitation> <dcterms:rights rdf:resource="http://nbn-resolving.org/urn:nbn:de:bsz:352-20140905103416863-3868037-7"/> <dcterms:abstract xml:lang="eng">Tmeda-coordinated species [(N,O)NiCH3(tmeda)] (tmeda = N,N,N′,N′-tetramethylethylenediamine), obtained by reaction of [(tmeda)NiMe2] with salicylaldimines, (O)H, are reactive and versatile intermediates for olefin polymerization catalysis. Solution NMR spectroscopic studies of 1-tmeda (N,O= 2,6-(3,5-(F3C)2C6H3)2C6H3-N═CH-(3,5-I2-2-OC6H2)) revealed two major binding modes of the tmeda ligand, open κ1- and, unexpectedly, chelating κ2-fashion, which interconvert slowly on the NMR chemical shift time scale, and form equilibria with solvent complexes 1-L (L= dmso, methanol). Binding of tmeda is favored by 2−3 orders of magnitude at the temperatures studied (25 to 80 °C) over binding of solvent. Chelating κ2-coordination of tmeda renders the monoanionic bidentate salicylaldiminato ligand κ1-coordinate. Exposure of dmso solutions of 1-tmeda to excess ethylene in an NMR tube at 55 °C resulted in the very minor formation of propylene and an equilibrium mixture of Ni(II)-ethyl complexes 2-dmso and [(κ1-N,O)Ni(αCH2βCH3)(κ2-tmeda)] (2-κ2-tmeda). Ethylene is primarily dimerized to butenes, which qualitatively parallels the reactivity observed for tmeda-free solutions of 2-dmso, but tmeda-coordinated Ni(II)-alkyl complexes appeared unreactive, i.e., dormant, toward ethylene. Carrying out the aforementioned reaction under aqueous conditions revealed that hydrolysis of Ni(II)-Me species to methane is a relevant deactivation pathway of the catalyst precursor, which clearly contrasts the reactivity observed in the absence of tmeda. Observed pseudo-first-order rate constants of overall disappearance of 1-tmeda split into two independent contributions according to kobs,Me,1-tmeda= kins,Me,1-tmeda + khydr,1-tmeda[water], khydr,1-tmeda= 1.9 × 10−4 M−1 s−1, and kins,Me,1-tmeda ≈ 2.4 × 10−4 M−1 s−1 (0.1 M [C2H4]). Determination of activation parameters of the bimolecular elimination of ethane from 1-tmeda (ΔH= 97 ± 7 kJ mol−1 and ΔS ≈ −5 J mol−1 K−1), a generally relevant deactivation mechanism of Ni(II)-methyl complexes, points out that tmeda-coordinated Ni(II)-methyl complexes, despite being inactive toward activation with ethylene, are actively involved in decomposition reactions.</dcterms:abstract> <dcterms:issued>2009</dcterms:issued> <dcterms:available rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2011-03-22T17:54:51Z</dcterms:available> <dc:contributor>Mecking, Stefan</dc:contributor> </rdf:Description> </rdf:RDF>

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