Low-spin 1,1′-diphosphametallocenates of chromium and iron

Greer, Samuel M.; Üngör, Ökten; Beattie, Ross J.; Kiplinger, Jaqueline L.; Scott, Brian L.; Stein, Benjamin W.; Goodwin, Conrad A. P.

doi:10.1039/d0cc06518h

“…The EPR spectra of 2a and 2b distinctly differ from the data obtained for "ferrocene-substituted radical anions," which exhibit narrow signals with well-resolved 1 H couplings and symmetry for the center of the spectra. 16 Similar to other low-spin Fe I complexes 56 including 1,1-diphosphaferrocenate, 20 the slightly rhombic spectra of 2a and 2b with comparatively wider and anisotropic signals are consistent with iron d-orbital character of the S = 1/2 ground state. We also performed 57 Fe Mössbauer spectroscopy of each compound in benzene or toluene solutions (Figure 3b).…”

Section: Resultssupporting

confidence: 70%

“…[15][16] Based on the fact that their high instability is caused by the dissociation of the cyclopentadienyl ligand, many attempts have been made to synthesize an isolobal structure of ferrocenate stabilized by the introduction of other ligands. [17][18][19][20][21][22][23][24] Astruc et al reported the synthesis of an iron-based sandwich complex [Fe(Cp)(η 6 -C6Me6)] 21 and its derivatives. 22 Tatsumi et al reported [(Cp*)Fe(μ-polyarene)Fe(Cp*)] complexes obtained by the reduction of half-sandwich Fe(II)Cp* compounds using potassium polyarenides.…”

Section: Introductionmentioning

confidence: 99%

Pyrrolinium-Substituted Persistent Zwitterionic Ferrocenate Derivative Enabling the Application of Ferrocene Anolyte

Song

¹

,

Kwon

²

,

Citek

³

et al. 2021

ACS Appl. Mater. Interfaces

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Here, we report the imidazolium-/pyrrolinium-substituted persistent zwitterionic ferrocenate derivatives, which were characterized by electron paramagnetic resonance (EPR) and 57 Fe Mössbauer spectroscopy. Additional theoretical studies on these zwitterionic ferrocenate derivatives clearly explain the origin of their thermal stability and the orbital interactions between iron and imidazolium-/pyrrolinium-substituted zwitterionic cyclopentadienyl ligand. Exploiting the facile Fe(II/I) redox chemistry, we successfully demonstrated that the ferrocene derivative can be applied as an example of derivatized ferrocene anolyte for redox-flow batteries. These zwitterionic ferrocenate derivatives will not only deepen our understanding of the intrinsic chemistry of ferrocenate but have the potential to open the way for the rational design of metallocenate derivatives for various applications. electrochemistry based on Fe(I)/Fe(II) ferrocene redox couples is feasible in practical battery operation and is enabled by the stereoelectronic stabilization of pyrrolinium-substituted zwitterionic ferrocenate derivative. ConclusionsFerrocene, one of the most representative compounds in the discipline of organometallic chemistry, attracted much attention because of its extremely high thermodynamic, chemical, and Fe(II/III) redox stability. However, the applications using the extremely negative voltage of ferrocene have not been reported to date due to the fast dissociation of the cyclopentadienyl anion ligands from Fe(I). Thus, an Fe(I) biscyclopentadiene complex remained elusive for a long time. Here, we have shown that zwitterionic ferrocenate derivatives 2a and 2b can be prepared by the one-electron reduction of 1a and 1b at ambient conditions, as confirmed by several complementary spectroscopic and theoretical methods. Additionally, a potential application in a redox-flow battery was successfully demonstrated using 1b as an example of ferrocene anolyte, in part due to the high degree of stabilization of low-valent state by the cAAC moiety. These imidazolium-/pyrrolinium-substituted ferrocene derivatives may deepen our understanding of the electrochemical behavior of ferrocene compounds and open the way to the rational design of ferrocenate derivatives. ASSOCIATED CONTENTSupporting Information. Experimental details, X-ray crystallographic analysis, Computational details, and other characterization data. The crystallographic data for 1a and 1b are deposited in the Cambridge Crystallographic Data Centre (CCDC) with deposition numbers CCDC 1940623 and 1940622. This material is available free of charge via the Internet at http://pubs.acs.org.

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“…[15][16] Based on the fact that their high instability is caused by the dissociation of the cyclopentadienyl ligand, many attempts have been made to synthesize an isolobal structure of ferrocenate stabilized by the introduction of other ligands. [17][18][19][20][21][22][23][24] Astruc et al reported the synthesis of an iron-based sandwich complex [Fe(Cp)(η 6 -C6Me6)] 21 and its derivatives. 22 Tatsumi et al reported [(Cp*)Fe(μ-polyarene)Fe(Cp*)] complexes obtained by the reduction of half-sandwich Fe(II)Cp* compounds using potassium polyarenides.…”

Section: Introductionmentioning

confidence: 99%

Pyrrolinium-substituted Persistent Zwitterionic Ferrocenate Derivative Enabling the Application of Ferrocene Anolyte

Song¹,

Kwon²,

Citek³

et al. 2021

Preprint

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Here, we report the imidazolium-/pyrrolinium-substituted persistent zwitterionic ferrocenate derivatives, which were characterized by electron paramagnetic resonance (EPR) and <sup>57</sup>Fe Mössbauer spectroscopy. Additional theoretical studies on these zwitterionic ferrocenate derivatives clearly explain the origin of their thermal stability and the orbital interactions between iron and imidazolium-/pyrrolinium-substituted zwitterionic cyclopentadienyl ligand. Exploiting the facile Fe(II/I) redox chemistry, we successfully demonstrated that the ferrocene derivative can be applied as an example of derivatized ferrocene anolyte for redox-flow batteries. These zwitterionic ferrocenate derivatives will not only deepen our understanding of the intrinsic chemistry of ferrocenate but have the potential to open the way for the rational design of metallocenate derivatives for various applications.

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“…Furthermore, isolation of 8 and the room‐temperature stable bis‐phospholyl [K(2.2.2‐cryptand)][Fe(PC 4 Me 4 ) 2 ] ( 15 ) [12] leads to the inference that the presence of an appropriate heteroatom in the ring can stabilize unusual oxidation states of the first‐row transition metals. Extensive studies on dicationic and monoanionic ferrocene ions throw light on how controlling the substituents on the C 5 ring as well as choosing appropriate redox environments can afford previously believed to be difficult synthetic targets [5, 10, 12, 13] . Making these anions stable at room temperature will be the next step in this area of research, which does not seem to be too far away.…”

Section: Figurementioning

confidence: 99%

The Redox Journey of Iconic Ferrocene: Ferrocenium Dications and Ferrocenate Anions

Walawalkar

¹

,

Pandey

²

,

Murugavel

³

2021

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Low-spin 1,1′-diphosphametallocenates of chromium and iron

Abstract: We report two low-spin diphosphametallocenates [K(2.2.2-crypt)][M(PC4Me4)2] (M = Cr, Fe) and propose structural features that allow spin-control in 3d metallocenates.

Cited by 13 publications

References 52 publications

Pyrrolinium-Substituted Persistent Zwitterionic Ferrocenate Derivative Enabling the Application of Ferrocene Anolyte

Pyrrolinium-Substituted Persistent Zwitterionic Ferrocenate Derivative Enabling the Application of Ferrocene Anolyte

Pyrrolinium-substituted Persistent Zwitterionic Ferrocenate Derivative Enabling the Application of Ferrocene Anolyte

The Redox Journey of Iconic Ferrocene: Ferrocenium Dications and Ferrocenate Anions

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