ESR investigations of complexes of niobium(IV) chloride with oxygen donors

Johnson, D. P.; Bereman, Robert D.

doi:10.1016/0022-1902(72)80608-0

Cited by 9 publications

(3 citation statements)

References 3 publications

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“…The ten-line pattern is consistent with hyperfine coupling of the unpaired electron to the I = 9/2 niobium nucleus (a Nb = 20 G). 14,15 In the cases of both 3-Ta and 3-Nb, the hyperfine coupling constants are less than 20% of the value normally associated with a classical metal-localized unpaired electron (i.e., M IV oxidation state), suggesting that the upaired electron is localized primarily on the (ONO) ligand. In contrast to 3-Ta and 3-Nb, the EPR signal for 3-V is shifted to g = 1.931 and displays an eight-line pattern due to a 70 G hyperfine coupling to the I = 7/2 vanadium center.…”

Section: Resultsmentioning

confidence: 97%

Metal effects on ligand non-innocence in Group 5 complexes of the redox-active [ONO] pincer ligand

et al. 2014

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Isostructural vanadium, niobium and tantalum complexes of bis(3,5-di-tert-butyl-2-phenol)amine ([ONO]H3), were prepared and characterized to evaluate the impact of the metal ion on redox-activity of the ligand platform. New vanadium and niobium complexes with the general formula, [ONO]MCl2L (M = V, L = THF, 1-V; M = Nb, L = Et2O, 1-Nb) were prepared and structurally analysed by X-ray crystallography. The solid-state structures indicate that the niobium derivative is electronically analogous to the tantalum analog 1-Ta, containing a reduced (ONO) ligand and a niobium(V) metal ion, [ONO(cat)]Nb(V)Cl2(OEt2); whereas, the vanadium derivative is best described as a vanadium(IV) complex, [ONO(sq)]V(IV)Cl2(THF). One-electron oxidation was carried out on all three metal complexes to afford [ONO]MCl3 derivatives (3-V, 3-Nb, 3-Ta). For all three derivatives, oxidation occurs at the (ONO) ligand. In the cases of niobium and tantalum, electronically similar complexes characterized as [ONO(sq)]M(V)Cl3 were obtained and for vanadium, ligand-based oxidation led to the formation of a complex best described as [ONO(q)]V(IV)Cl3. All complexes were characterized by spectroscopic and electrochemical methods. DFT and TD-DFT calculations were used to probe the electronic structure of the complexes and help verify the different electronic structures stemming from changes to the coordinated metal ion.

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Section: Resultsmentioning

confidence: 97%

Metal effects on ligand non-innocence in Group 5 complexes of the redox-active [ONO] pincer ligand

et al. 2014

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“…19 A body of spectroscopic and magnetic studies have suggested that NbCl 4 (THF) 2 exists as a paramagnetic (d 1 ) monomer with THF molecules arranged in a cis fashion in the solid state with trans geometry observed in solution. 20,21 For NbCl 3 (DME), on the other hand, there is no definitive answer whether this complex exists in monomeric form, with conflicting reports describing it as either mononuclear 22 or polymeric. 23,24 The absence of a single crystal X-ray structure of this compound is most likely a consequence of its high reactivity toward any solvent that it is soluble in.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Their formulas, as written above and most often referred to in the literature, are somewhat misleading because only NbCl 5 has been structurally characterized and shown to exist itself in the solid state as discrete Nb 2 Cl 10 dimers . A body of spectroscopic and magnetic studies have suggested that NbCl 4 (THF) 2 exists as a paramagnetic (d 1 ) monomer with THF molecules arranged in a cis fashion in the solid state with trans geometry observed in solution. , For NbCl 3 (DME), on the other hand, there is no definitive answer whether this complex exists in monomeric form, with conflicting reports describing it as either mononuclear or polymeric. , The absence of a single crystal X-ray structure of this compound is most likely a consequence of its high reactivity toward any solvent that it is soluble in . A structural understanding would be valuable not only for the rational synthesis of other Nb(III) complexes but also for comprehension of its catalytic performance, such as in [2 + 2 + 2] cycloadditions. − All precursors would benefit from a rigorous description of their structures, given the current emphasis on precise engineering of materials at the atomic level, from custom materials synthesis to niobium doping.…”

Section: Introductionmentioning

confidence: 99%

Molecular Niobium Precursors in Various Oxidation States: An XAS Case Study

et al. 2018

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Although X-ray absorption spectroscopy (XAS) has become an indispensable tool in characterization of solidstate materials, it is less of a staple in molecular chemistry of niobium. Scattering X-ray techniques remain relatively unexplored for the systematic study of molecular niobium compounds. Here, we use XAS to probe the niobium environment in commonly used Nb precursors in +V, +IV, and +III oxidation states. Apart from laying out the guidelines for identification of niobium oxidation states, we correlate our data with density functional theory models to provide further structural insight. Of particular note, we are able to shed light on the nature of the commonly used and catalytically competent NbCl 3 (DME), which had not been previously characterized structurally despite its prevalence in Nb chemistry.

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2.4 References to electron paramagnetic resonance data and diagrams

König¹,

König²

Magnetic Properties of Coordination and Organometallic Transition Metal Compounds

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ESR investigations of complexes of niobium(IV) chloride with oxygen donors

Cited by 9 publications

References 3 publications

Metal effects on ligand non-innocence in Group 5 complexes of the redox-active [ONO] pincer ligand

Metal effects on ligand non-innocence in Group 5 complexes of the redox-active [ONO] pincer ligand

Molecular Niobium Precursors in Various Oxidation States: An XAS Case Study

2.4 References to electron paramagnetic resonance data and diagrams

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