1. Mixed valence triiron complexes from the conjugation of [FeIFeI] and [FeII] complexes via intermolecular carbyne/alkyne coupling.
- Author
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Bresciani, Giulio, Ciancaleoni, Gianluca, Zacchini, Stefano, Biancalana, Lorenzo, Pampaloni, Guido, Funaioli, Tiziana, and Marchetti, Fabio
- Subjects
NUCLEAR magnetic resonance spectroscopy ,CYCLIC voltammetry ,SINGLE crystals ,ACETONITRILE ,X-ray diffraction ,ELECTROLYTIC reduction - Abstract
We present a new synthetic strategy for obtaining mixed-valence triiron complexes where the metal centers are bridged by a novel, highly functionalized hydrocarbyl ligand. The alkynyl–vinyliminium complexes [Fe
2 Cp2 (CO)(μ-CO){μ-η1 :η3 -C(X–C≡CH)CHCNMe2 }]CF3 SO3 (X = 4-C6 H4 , [2a1]CF3 SO3 ; X = (CH2 )3 , [2a2]CF3 SO3 ) were synthesized in almost quantitative yields from the aminocarbyne precursor [Fe2 Cp2 (CO)2 (μ-CO){μ-CNMe2 }]CF3 SO3 , [1a]CF3 SO3 , and the di-alkynes HC≡C–X–C≡CH. Then, the ferracycle [Fe(Cp)(CO){C(NMe2 )CH=C(4-C6 H4 C≡CH)C(O)}], 4a1, was produced in 47% yield from the cleavage of [2a1]CF3 SO3 promoted by pyrrolidine. Subsequent reactions of the acetonitrile adducts [Fe2 Cp2 (CO)(μ-CO)(NCMe){μ-CNMe(R)}]CF3 SO3 (R = Me, [1aACN ]CF3 SO3 ; R = Xyl, [1bACN ]CF3 SO3 ) ([FeI FeI ]) with 4a1 ([FeII ]) at room temperature resulted in the formation of [FeI FeI FeII ] complexes [Fe2 Cp2 (CO)(μ-CO){μ-η1 :η3 -C(X–C=CHC(NMe2 )=FeCp(CO)C=O)CHCNMe(R)}]CF3 SO3 (R = Me, [5a1]CF3 SO3 ; R = Xyl, [5b1]CF3 SO3 ) in yields ranging from 56% to 64%. The new products were characterized by IR and multinuclear NMR spectroscopy, and the structures of [2a2]CF3 SO3 and 4a1 were confirmed by single crystal X-ray diffraction. Cyclic voltammetry and spectroelectrochemical studies on [5a1]+ have revealed that reduction and oxidation events occur almost independently at the [FeI FeI ] and [FeII ] units, respectively. This observation underscores a minimal electronic interaction between the two fragments within the triiron complex. Accordingly, DFT studies pointed out that the HOMO and LUMO orbitals are predominantly localized in the two distinct compartments of [5a1]+ . [ABSTRACT FROM AUTHOR]- Published
- 2024
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