Dinuclear Group IV Metal Complexes based on a Bis(indenyl)-(E/Z)-Stilbene Platform: A Potential Prototype of “Photoswitchable” Catalysts for Olefin Polymerization - INSA Rennes - Institut National des Sciences Appliquées de Rennes Access content directly
Journal Articles Dalton Transactions Year : 2024

Dinuclear Group IV Metal Complexes based on a Bis(indenyl)-(E/Z)-Stilbene Platform: A Potential Prototype of “Photoswitchable” Catalysts for Olefin Polymerization

Abstract

The preparation of dizirconium complexes based on a novel bis(indenyl)-(E/Z)-stilbene platform was explored. Negishi coupling between the in situ-generated diorganozincates obtained from the respective o/m/p-(E/Z)-dibromostilbenes and the bromo-functionalized zirconocene (η5-Cp*)(η5-2-methyl-4-bromoindenyl)ZrCl2, or, alternatively, the preparation of bis(indene)stilbene pro-ligands {o/m/p-(E/Z)-BisIndSB}H2 through Negishi coupling of the corresponding dibromostilbenes with 4-bromoindene and subsequent metallation/transmetallation with Cp*ZrCl3 or Zr(NMe2)4, allowed the preparation of a series of dinuclear complexes. These were analyzed by NMR spectroscopy and some of them by iASAP-mass spectrometry and by X-ray diffraction studies. Experimental results were compared with DFT modelling of the targeted dinuclear complexes evidencing that the (E)-complexes are more stable by 7–11 kcal mol−1 than their (Z)-analogues. Thermal, uncontrolled isomerization of (Z)- to (E)-stilbene platform was observed experimentally for some systems, in the course of their synthesis, either from the (Z)-dibromostilbene reagent or on the dinuclear complexes resulting from the Negishi coupling. Photoisomerization of the (E)- and (Z)-{BisIndSB}H2 proligands and of complexes {o-(E)-BisIndSB}(Zr(NMe2)3)2 and {m-(E)-BisIndSB}(ZrCl2Cp*)2 was investigated under a variety of conditions. It proved effective for the proligands but induced decomposition of the dizirconium complexes. Time-dependent DFT (TD-DFT) computations were performed to identify unambiguously the nature of the observed absorption bands and account for decomposition of the complexes. Preliminary ethylene/1-hexene homo- and copolymerization investigations did not evidence putative cooperativity phenomena within these dinuclear systems nor significantly differentiated behavior between the (Z)- and (E)-isomers of a given type of complex under the reaction conditions investigated.
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hal-04614239 , version 1 (17-06-2024)

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Nuria Romero, Thierry Chavagnan, Thierry Roisnel, Alexandre Welle, Evgueni Kirillov, et al.. Dinuclear Group IV Metal Complexes based on a Bis(indenyl)-(E/Z)-Stilbene Platform: A Potential Prototype of “Photoswitchable” Catalysts for Olefin Polymerization. Dalton Transactions, 2024, 53, pp.9452-9466. ⟨10.1039/d4dt00498a⟩. ⟨hal-04614239⟩
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