Der Carboxylat‐Twist – Aufklärung hysteretischer Bistabilität eines High‐Spin‐Dieisen(II)‐Komplexes mithilfe von Mößbauer‐Spektroskopie

Burger, Boris; Demeshko, Serhiy; Bill, Eckhard; Dechert, Sebastian; Meyer, Franc

doi:10.1002/ange.201202759

Angewandte Chemie

2012

DOI: 10.1002/ange.201202759

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Der Carboxylat‐Twist – Aufklärung hysteretischer Bistabilität eines High‐Spin‐Dieisen(II)‐Komplexes mithilfe von Mößbauer‐Spektroskopie

Boris Burger

Serhiy Demeshko

Eckhard Bill

et al.

Abstract: In der Zange eines präorganisierten Dieisen(II)‐Gerüsts zeigt ein Carboxylatligand temperaturabhängiges dynamisches Verhalten („Carboxylat‐Twist“; siehe Schema). Die Kippbewegung bedingt eine Fluktuation des elektrischen Feldgradienten und somit gemittelte Mößbauer‐Resonanzen bei höherer Temperatur. Der Prozess führt, ohne Beteiligung von Spin‐Crossover oder Valenztautomerie, zu magnetischer und spektroskopischer Hysterese.

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Cited by 3 publications

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A Two‐in‐one Pincer Ligand and its Diiron(II) Complex Showing Spin State Switching in Solution through Reversible Ligand Exchange

Samanta¹,

Demesko²,

Dechert³

et al. 2014

Angewandte Chemie

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A novel pyrazolate-bridged ligand providing two {PNN} pincer-type compartments has been synthesized. Its diiron(II) complex LFe 2 (OTf) 3 (CH 3 CN) (1; Tf= triflate) features, in solid state, two bridging triflate ligands, with a terminal triflate and a MeCN ligand completing the octahedral coordination spheres of the two high-spin metal ions. In MeCN solution, 1 is shown to undergo a sequential, reversible, and complete spin transition to the low-spin state upon cooling. Detailed UV/Vis and 19 F NMR spectroscopic studies as well as magnetic measurements have unraveled that spin state switching correlates with a rapid multistep triflate/ MeCN ligand exchange equilibrium. The spin transition temperature can be continuously tuned by varying the triflate concentration in solution.

show abstract

A Two‐in‐one Pincer Ligand and its Diiron(II) Complex Showing Spin State Switching in Solution through Reversible Ligand Exchange

Samanta¹,

Demesko²,

Dechert³

et al. 2014

Angewandte Chemie

Self Cite

View full text Add to dashboard Cite

show abstract

A Two‐in‐one Pincer Ligand and its Diiron(II) Complex Showing Spin State Switching in Solution through Reversible Ligand Exchange

Samanta¹,

Demesko²,

Dechert³

et al. 2014

Angew Chem Int Ed

Self Cite

View full text Add to dashboard Cite

A novel pyrazolate-bridged ligand providing two {PNN} pincer-type compartments has been synthesized. Its diiron(II) complex LFe2(OTf)3(CH3CN) (1; Tf = triflate) features, in solid state, two bridging triflate ligands, with a terminal triflate and a MeCN ligand completing the octahedral coordination spheres of the two high-spin metal ions. In MeCN solution, 1 is shown to undergo a sequential, reversible, and complete spin transition to the low-spin state upon cooling. Detailed UV/Vis and (19)F NMR spectroscopic studies as well as magnetic measurements have unraveled that spin state switching correlates with a rapid multistep triflate/MeCN ligand exchange equilibrium. The spin transition temperature can be continuously tuned by varying the triflate concentration in solution.

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Mononuclear or Dinuclear? Mechanistic Study of the Zinc‐Catalyzed Oxidative Coupling of Aldehydes and Acetylenes

Yue

Bai

et al. 2017

Chemistry A European J

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Although zinc catalysis is widely used in organic synthesis, very few studies on the dinuclear zinc mechanism have been reported. Here, a dinuclear zinc pathway is proposed for the Zn(OTf) -catalyzed oxidative coupling of aldehydes with terminal alkynes. DFT calculations revealed that the deprotonation of the terminal alkyne would preferentially lead to the formation of a dinuclear zinc intermediate. The nucleophilic addition of this intermediate to an aldehyde, followed by an Oppenauer-type oxidation was investigated theoretically according to the mono- and dinuclear pathways. The formation of a dinuclear zinc intermediate from a mononuclear alkynyl zinc complex was exergonic, favoring the dinuclear zinc pathway. The subsequent protonation and regeneration of the active dinuclear catalyst were also evaluated by DFT calculations. The oxidizabilities of various aldehydes and ketones were evaluated to determine the best oxidant for this step. Trifluoroacetaldehyde was predicted to be a better oxidant for this reaction because its calculated energy barrier for the Oppenauer-type oxidation step was much lower than that of the other carbonyl complexes.

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Der Carboxylat‐Twist – Aufklärung hysteretischer Bistabilität eines High‐Spin‐Dieisen(II)‐Komplexes mithilfe von Mößbauer‐Spektroskopie

Cited by 3 publications

References 28 publications

A Two‐in‐one Pincer Ligand and its Diiron(II) Complex Showing Spin State Switching in Solution through Reversible Ligand Exchange

A Two‐in‐one Pincer Ligand and its Diiron(II) Complex Showing Spin State Switching in Solution through Reversible Ligand Exchange

A Two‐in‐one Pincer Ligand and its Diiron(II) Complex Showing Spin State Switching in Solution through Reversible Ligand Exchange

Mononuclear or Dinuclear? Mechanistic Study of the Zinc‐Catalyzed Oxidative Coupling of Aldehydes and Acetylenes

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