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[Re(η6-arene)2]+ as a highly stable ferrocene-like scaffold for ligands and complexes


Hernández-Valdés, Daniel; Avignon, Frédéric; Müller, Peter; Meola, Giuseppe; Probst, Benjamin; Fox, Thomas; Spingler, Bernhard; Alberto, Roger (2020). [Re(η6-arene)2]+ as a highly stable ferrocene-like scaffold for ligands and complexes. Dalton Transactions, 49(16):5250-5256.

Abstract

Ferrocenes are versatile ligand scaffolds, complexes of which have found numerous applications in catalysis. Structurally similar but of higher redox stabilites are sandwich complexes of the [Re(η6-arene)2]+ type. We report herein routes for conjugating potential ligands to a single or to both arenes in this scaffold. Since the arene rings can freely rotate, the [Re(η6-arene)2]+ has a high degree of structural flexibility. Polypyridyl ligands were successfully introduced. The coordination of Co(II) to such a model tetrapyridyl-Re(I)-bis-benzene complex produced a bimetallic Re(I)–Co(II) complex. To show the stability of the resulting architecture, a selected complex was subjected to photocatalytic reactions. It showed good activity in proton reduction over a long time and did not decompose, corroborating its extraordinary stability even under light irradiation. Its activity compares well with the parent catalyst in turn over numbers and frequencies. The supply of electrons limits catalytic turnover frequency at concentrations below ∼10 μM. We also show that other ligands can be introduced along these strategies. The great diversity offered by [Re(η6-arene)2]+ sandwich complexes from a synthetic point allows this concept to be extended to other catalytic processes, comparable to ferrocenes.

Abstract

Ferrocenes are versatile ligand scaffolds, complexes of which have found numerous applications in catalysis. Structurally similar but of higher redox stabilites are sandwich complexes of the [Re(η6-arene)2]+ type. We report herein routes for conjugating potential ligands to a single or to both arenes in this scaffold. Since the arene rings can freely rotate, the [Re(η6-arene)2]+ has a high degree of structural flexibility. Polypyridyl ligands were successfully introduced. The coordination of Co(II) to such a model tetrapyridyl-Re(I)-bis-benzene complex produced a bimetallic Re(I)–Co(II) complex. To show the stability of the resulting architecture, a selected complex was subjected to photocatalytic reactions. It showed good activity in proton reduction over a long time and did not decompose, corroborating its extraordinary stability even under light irradiation. Its activity compares well with the parent catalyst in turn over numbers and frequencies. The supply of electrons limits catalytic turnover frequency at concentrations below ∼10 μM. We also show that other ligands can be introduced along these strategies. The great diversity offered by [Re(η6-arene)2]+ sandwich complexes from a synthetic point allows this concept to be extended to other catalytic processes, comparable to ferrocenes.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Scopus Subject Areas:Physical Sciences > Inorganic Chemistry
Uncontrolled Keywords:Inorganic Chemistry
Language:English
Date:1 January 2020
Deposited On:03 Apr 2020 10:22
Last Modified:03 May 2021 15:23
Publisher:Royal Society of Chemistry
ISSN:1477-9226
OA Status:Hybrid
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1039/d0dt00731e
Project Information:
  • : FunderSNSF
  • : Grant IDIZLSZ2_170856
  • : Project TitleSolar Light-driven Homogeneous Catalysis for Greener Industrial Processes with H2 as Energy Source and CO2 as C1 Building Block

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