2020
DOI: 10.1021/acs.inorgchem.9b03665
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Bis(imino)pyrazine-Supported Iron Complexes: Ligand-Based Redox Chemistry, Dearomatization, and Reversible C–C Bond Formation

Abstract: Iron complexes supported by novel π-acidic bis­(imino)­pyrazine (PPzDI) ligands can be functionalized at the nonligated nitrogen atom, and this has a marked effect on the redox properties of the resulting complexes. Dearomatization is observed in the presence of cobaltocene, which reversibly reduces the pyrazine core and not the imine functionality, as observed in the case of the pyridinediimine-ligated iron analogues. The resulting ligand-based radical is prone to dimerization through the formation of a long … Show more

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Cited by 17 publications
(31 citation statements)
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“…[21] Themolecular structure of 7 reveals that the pyrazine ring retains its aromaticity [22] and is essentially flat. TheN -Ca-C angle is nevertheless compressed (]114.29 14 119.03(18) in 1•[I] [8] ). Them agnitude of the angle compression is similar to the one in the analogous isoquinolin-1ylidine rhodium(I) complexes.…”
Section: Resultsmentioning
confidence: 99%
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“…[21] Themolecular structure of 7 reveals that the pyrazine ring retains its aromaticity [22] and is essentially flat. TheN -Ca-C angle is nevertheless compressed (]114.29 14 119.03(18) in 1•[I] [8] ). Them agnitude of the angle compression is similar to the one in the analogous isoquinolin-1ylidine rhodium(I) complexes.…”
Section: Resultsmentioning
confidence: 99%
“…[4][5][6] Nevertheless, the prevalence of ferrocene as ar edox-switch narrows the potential-window needed to be applied for the redox chemistry to occur,making them largely dependent on those of the Fc 0 /Fc + (Fc = ferrocene) couple.H erein, we wish to introduce an ew,n on-ferrocene based redox-active carbene architecture,w hich makes use of aF e 0 -ligated pyrazinediimine ligand (P Pz DI), where both the iron centre and the ligand framework can be involved in the redox activity. [8] We envisaged that the new ligand scaffold would offer the following advantages: (a) as the formally Fe 0 centre in PDI/ P Pz DI-type ligands (PDI = pyridinediimine,P Pz DI = pyrazinediimine) is more easily oxidised than the Fe II centre in ferrocene,m ilder oxidation conditions would allow access to the oxidised form [9] (b) while in ferrocene,t he iron centre is more reluctant to engage in reactivity,i ron-PDI complexes display very rich chemistry ranging from catalysis to small molecule activation, making them the systems of choice for ac onsiderable number of transformations [10] (c) the P Pz DIligand is itself redox active through the reversible reduction of the imine functionality or ligand core,t herefore allowing access to more redox states.Herein, we wish to communicate the synthesis of the new iron-P Pz DI NHC-like precursors,the redox chemistry of the corresponding rhodium complexes and examples of reversible alcohol and amine activation at the in situ generated carbene centre.…”
Section: Introductionmentioning
confidence: 99%
“…[20] Die molekularen Strukturen von 7 und 8 konnten durch Einkristallrçntgenstrukturanalyse aufgeklärt werden (Abbildung 1). [21] Die Struktur von 7 zeigt, dass der Pyrazinring seine Aromatizitätb ehält [22] und eine planare Struktur aufweist.Der N-Ca-C Winkel ist dennoch verkleinert (]114.29-(14)8 8 in 7,v erglichen mit 119.03(18) in 1•[I] [8] ). Das Ausmaß der Winkelverkleinerung ist vergleichbar mit analogen Isochinolin-1-ylidin-Rhodium(I)-Komplexen.…”
Section: Ergebnisse Und Diskussionunclassified
“…Dabei konvergierten alle Experimente zu einem BS (0,0) (d. h. alle Elektronen gepaart) Zustand, wie auch schon fürd ie Ausgangsverbindung 1•[I] und (P Pz DI)Fe(CO) 2 . [8] Dies lässt auf ein Fe 0 mit neutralem P Pz DI-Liganden schließen, was mit dem fürd iese komplexe beobachteten Diamagnetismus in Einklang steht. Die qunantenchemisch erzeugten Molekülorbitale (Abbildung 5) des freien Carbens 2,speziell HOMO und LUMO,s ind energetisch und morphologisch ähnlich denen des (P Pz DI)Fe(CO) 2 ,m it einem geringen HOMO-LUMO Abstand von 2.60 eV,e rklärbar durch die ausgeprägte Delokalisierung des p -Systems durch den Pyrazinring und die Imin-Funktionalitäten.…”
Section: Angewandte Chemieunclassified
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