Diamagnetic–Paramagnetic Conversion of Tris(2‐pyridylthio)methylcopper(III) through a Structural Change from Trigonal Bipyramidal to Octahedral

Santo, R.; Miyamoto, Riichi; Tanaka, Rika; Nishioka, Takanori; Sato, Kazunobu; Toyota, Kazuo; Obata, Makoto; Yano, Shigenobu; Kinoshita, Isamu; Ichimura, Akio; Takui, Takeji

doi:10.1002/ange.200603127

Cited by 14 publications

(15 citation statements)

References 32 publications

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“…The same conclusions were recently drawn by Kinoshita et al for a related, though intramolecularly coordinating, www.chemeurj.org ambidentate ligand and its copper and zinc complexes. [1,51] Based on our experimental and DFT studies, we have therefore assumed the metal-centred redox processes shown in Equation (5) for 3 and 4 during our discussion of the electrochemical findings, and present the first experimental evidence.…”

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confidence: 99%

Syntheses, Structures and Electronic Properties of Zwitterionic Iron(II) and Cobalt(II) Complexes Featuring Ambidentate Tris(pyrazolyl)methanide Ligands

Kuzu

Krummenacher

Hewitt

et al. 2009

Chemistry A European J

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By deprotonation of the corresponding tris(pyrazolyl)methane ((Me)Tpm) precursor complexes [M((Me)Tpm)(2)][(OTf)(2)] (1 and 2), the zwitterionic tris(pyrazolyl)methanide iron(II) (3) and cobalt(II) (4) "sandwich" complexes of the general formula [M((Me)Tpmd)(2)] are easily accessible. The structurally characterised complexes 3 and 4 are the first such homoleptic 3d transition metal species to feature two "naked", outward pointing pyramidal carbanions. Density functional theory calculations show metal-centred HOMOs and LUMOs with the destabilised carbanion orbitals in the energy region of the filled transition-metal-centred frontier orbitals. The electronic structures of these complexes have been investigated in detail by various spectroscopic techniques such as NMR, EPR, SQUID, Mössbauer, etc. Both complexes adopt a high-spin (HS) configuration at room temperature in solution and in the solid state. A thermally induced high-spin to low-spin (HS-LS) transition is observed for the iron(II) complex 3. The HS-LS transition temperature of 3 in solution differs from that in the solid state, which in turn strongly depends on the amount of solvent molecules in the crystal lattice. Electrochemical studies on the corresponding cobalt(II) complex 4 provide evidence for a HS-Co(II) <==> LS-Co(III) transition upon oxidation, which was confirmed by preliminary synthetic oxidation reactions. Overall, it can be concluded that the related kappa(3)N-donor ligands tris(pyrazolyl)hydroborates (Tp(R)) and (R)Tpmd ligands have similar bonding properties and that the metal cations experience more or less the same ligand environment.

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confidence: 99%

Syntheses, Structures and Electronic Properties of Zwitterionic Iron(II) and Cobalt(II) Complexes Featuring Ambidentate Tris(pyrazolyl)methanide Ligands

Kuzu

Krummenacher

Hewitt

et al. 2009

Chemistry A European J

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“…However, these compounds exhibited narrow isotropic EPR signals with g values of about 2.000 (which are characteristic of organic radicals) in the solid state at room temperature (see the Supporting Information, Figure S8). [22] Such a remarkable change indicates that stacking induces the formation of paramagnetic phenoxide-type radicals in the solid state (see the Supporting Information, Scheme S1). [22] Such a remarkable change indicates that stacking induces the formation of paramagnetic phenoxide-type radicals in the solid state (see the Supporting Information, Scheme S1).…”

Section: Resultsmentioning

confidence: 99%

Stacking‐Induced Diamagnetic/Paramagnetic Conversion of Imidazo[1,2‐a]pyridin‐2(3 H)‐one Derivatives: Near‐Infrared Absorption and Magnetic Properties in the Solid State

Yong

Zhang

Zhao

et al. 2013

Chemistry An Asian Journal

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Herein, we present three imidazo[1,2-a]pyridin-2(3 H)-one derivatives that are diamagnetic in solution, but paramagnetic in the solid state, possibly owing to a stacking-induced formation of phenoxide-type radicals. Notably, a larger bathochromic shift of the absorption (even up to the near- infrared region) of these three compounds was observed in the solid state than in solution, which was attributable to the ordered columnar stacking arrangements or their single-electron character as radicals in the solid state. Interestingly, compared to that in solution, (E)-3-(pyridin-4'-ylmethylene)imidazo[1,2-a]pyridine 2(3 H)-one displayed a largely red-shifted emission (centered at 660 nm, with tailing above 800 nm) in the solid state. A larger bathochromic shift (260 nm) of the emission is an indication of better order and tight stacking in the solid state, which is brought about by the rigid and polar acceptor. These three compounds also reveal different magnetic susceptibilities at 300 K, thus implying that they possess various columnar stacking structures. Most interestingly, these three radicals exhibit unusual ferromagnetic-to-antiferromagnetic phase transitions, which can be attributed to anisotropic contraction and non-uniform slippage of the columnar stacking chains.

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“…[127] Zudem wurde der erste direkte experimentelle Nachweis für die Beteiligung eines Cu III -Intermediats an einer Ullmann-Kupplung 2010 von Ribas und Stahl durch Verwendung eines makrocyclischen Arylhalogenid-Substrats erbracht. [128] [129][130][131][132][133] In den letzten Jahren wurden einige Kupfer(II)-und Kupfer(III)-Komplexe synthetisiert und kristallographisch charakterisiert, [134][135][136][137][138][139][140] und die erhaltenen Ergebnisse dienen als wichtige Grundlage bei der Betrachtung derartiger Intermediate in Cu-katalysierten Oxidationen. Mehrere dieser Komplexe wurden über Cu II -vermittelte Aktivierung einer C-H-Bindung eines Makrocyclus hergestellt.…”

Section: Hochvalente Organokupfer-komplexe In Nicht-oxidativen Reaktiunclassified

Kupferkatalysierte aerobe oxidative C‐H‐Funktionalisierungen: Trends und Erkenntnisse zum Mechanismus

2011

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Die selektive Oxidation von C‐H‐Bindungen und der Einsatz von O2 als stöchiometrisches Oxidationsmittel stellen zwei wesentliche Herausforderungen in der organischen Chemie dar. Kupfer(II) ist ein vielseitiges Oxidationsmittel für verschiedene oxidative Kupplungen, die durch Einelektronen‐Transfer (SET) von elektronenreichen organischen Molekülen ausgelöst werden. Viele dieser Reaktionen können mit Kupfer katalytisch durchgeführt werden, wenn molekularer Sauerstoff als Oxidationsmittel eingesetzt wird, um den aktiven Kupfer(II)‐Katalysator zu regenerieren. Daneben wurden auch zahlreiche neue Cu‐katalysierte C‐H‐Oxidationen mit elektronenarmen Substraten beschrieben, von denen ein SET zum Kupfer(II) unwahrscheinlich scheint. In einigen dieser Fälle konnte die Beteiligung von Organokupfer(III)‐Intermediaten im Reaktionsmechanismus nachgewiesen werden. Metallorganische C‐H‐Oxidationen dieser Art eröffnen neue bedeutende Möglichkeiten für das Gebiet der Cu‐katalysierten aeroben Oxidationen.

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Diamagnetic–Paramagnetic Conversion of Tris(2‐pyridylthio)methylcopper(III) through a Structural Change from Trigonal Bipyramidal to Octahedral

Cited by 14 publications

References 32 publications

Syntheses, Structures and Electronic Properties of Zwitterionic Iron(II) and Cobalt(II) Complexes Featuring Ambidentate Tris(pyrazolyl)methanide Ligands

Syntheses, Structures and Electronic Properties of Zwitterionic Iron(II) and Cobalt(II) Complexes Featuring Ambidentate Tris(pyrazolyl)methanide Ligands

Stacking‐Induced Diamagnetic/Paramagnetic Conversion of Imidazo[1,2‐a]pyridin‐2(3 H)‐one Derivatives: Near‐Infrared Absorption and Magnetic Properties in the Solid State

Kupferkatalysierte aerobe oxidative C‐H‐Funktionalisierungen: Trends und Erkenntnisse zum Mechanismus

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