A square-planar nickel(III) complex of an innocent ligand system

Collins, Terrence J.; Nichols, Thomas; Uffelman, Erich S.

doi:10.1021/ja00012a064

Cited by 100 publications

(70 citation statements)

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“…Selected bond lengths [pm] and angles [8] with estimated standard deviations: NiÀC(1) 191.9(5), NiÀC (7) 193.1(5), NiÀC (13) www.chemeurj.org 4 geometry. [34] Accordingly, mutually trans-standing groups are heavily staggered, and the whole [Ni…”

Section: Resultsmentioning

confidence: 99%

“…[5] Examples of redox-active ligands are also known with hard donor atoms (typically N or O) attached to unsaturated bond systems with p-delocalized electron density. [5][6][7] Even the innocence of ligands [8] bearing hard donor atoms and lacking (by design) the possibility of extended electron delocalization has been recently challenged. [9] Although suffering from certain limitations and ambiguities, the oxidation state concept (also known as oxidation number) is a widely extended and extremely useful convention.…”

Section: H T U N G T R E N N U N G [Ni IImentioning

confidence: 99%

“…Using Equation (3) with these wavefunctions would result in the principal g-values given in Equation (8).…”

Section: (1) a C H T U N G T R E N N U N G [Nbu 4 ]A C H T U N G T Rmentioning

confidence: 99%

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Homoleptic Organoderivatives of High‐Valent Nickel(III)

Alonso

Arauzo

García‐Monforte

et al. 2009

Chemistry A European J

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Homoleptic perhalophenyl derivatives of divalent nickel complexes with the general formula [NBu(4)](2)[Ni(II)(C(6)X(5))(4)] [X=F (1), Cl (2)] have been prepared by low-temperature treatment of the halo-complex precursor [NBu(4)](2)[NiBr(4)] with the corresponding organolithium reagent LiC(6)X(5). Compounds 1 and 2 are electrochemically related by reversible one-electron exchange processes with the corresponding organometallate(III) compounds [NBu(4)][Ni(III)(C(6)X(5))(4)] [X=F (3), Cl (4)]. The potentials of the [Ni(III)(C(6)X(5))(4)](-)/[Ni(II)(C(6)X(5))(4)](2-) couples are +0.07 and -0.11 V for X=F or Cl, respectively. Compounds 3 and 4 have also been prepared and isolated in good yield by chemical oxidation of 1 or 2 with bromine or the amminium salt [N(C(6)H(4)Br-4)(3)][SbCl(6)]. The [Ni(III)(C(6)X(5))(4)](-) species have SP-4 structures in the salts 3 and 4, as established by single-crystal X-ray diffraction methods. The [Ni(II)(C(6)F(5))(4)](2-) ion in the parent compound 1 has also been found to exhibit a rather similar SP-4 structure. According to their SP-4 geometry, the Ni(III) compounds (d(7)) behave as S=1/2 systems both at microscopic (EPR) and macroscopic levels (ac and dc magnetization measurements). The spin Hamiltonian parameters obtained from the analysis of the magnetic behavior of 3 and 4 within the framework of ligand field theory show that the unpaired electron is centered mainly on the metal atom, with >97 % estimated d(z(2) ) contribution. Thermal decomposition of 3 and 4 proceeds with formation of the corresponding C(6)X(5)--C(6)X(5) coupling compounds.

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Section: Resultsmentioning

confidence: 99%

Section: H T U N G T R E N N U N G [Ni IImentioning

confidence: 99%

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Homoleptic Organoderivatives of High‐Valent Nickel(III)

Alonso

Arauzo

García‐Monforte

et al. 2009

Chemistry A European J

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“…= 2.29, g k = 2.20) strongly indicate that the coordination environment of the nickel-(iii) ion is a distorted square-planar structure with a d z 2 ground state. [29] The cyclic voltammograms of 1 and 2 have been measured in CH 2 Cl 2 under anaerobic conditions and show two reversible redox waves (1: E 1/2a = 0.63 V and E 1/2b = 0.19 V, 2: E 1/2a = 0.59 V and E 1/2b = 0.10 V vs SCE). Taking into account the results of XPS data (Ni 2p 3/2 = 854.9 eV) as well as EPR signal (g = 2.0061), the first E 1/2a and the second E 1/2b redox waves of 1 are assigned to the Ni III /Ni II couple and the Cat/ SQ couple, respectively.…”

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confidence: 99%

Electronic Structural Changes between Nickel(II)–Semiquinonato and Nickel(III)–Catecholato States Driven by Chemical and Physical Perturbation

Ohtsu

Tanaka

2005

Chemistry A European J

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The selective synthesis of tetracoordinate square-planar low-spin nickel(II)-semiquinonato (Ni(II)-SQ) and nickel(III)-catecholato (Ni(III)-Cat) complexes, 1 and 2, respectively, was achieved by using bidentate ligands with modulated nitrogen-donor ability to the nickel ion. The electronic structures of 1 and 2 were revealed by XPS and EPR measurements. The absorption spectra of 1 and 2 in a noncoordinating solvent, dichloromethane (CH2Cl2), are completely different from those in tetrahydrofuran (THF), being a coordinating solvent. As expected from this result, the gradual addition of N,N-dimethylformamide (DMF), which is also a coordinating solvent like THF, into a solution of 1 or 2 in CH2Cl2 leads to color changes from blue (for 1) and brown (for 2) to light green, which is the same color observed for solutions of 1 or 2 in THF. Furthermore, the same color changes are induced by varying the temperature. Such spectral changes are attributable to the transformation from square-planar low-spin Ni(II)-SQ and Ni(III)-Cat complexes to octahedral high-spin Ni(II)-SQ ones, caused by the coordination of two solvent molecules to the nickel ion.

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“…= 2.29, g k = 2.20) provide valuable information about the coordination environment of the nickel(iii) ion, which is a distorted square-planar structure with a d z 2 ground state. [11] The oxidation states of nickel in 1 and 2 were further confirmed by X-ray photoelectron spectra. The observed binding energy of the Ni 2p 3/2 signals at 854.9 (1) and 856.1 eV (2) is consistent with oxidation states of Ni II and Ni III , respectively.…”

mentioning

confidence: 81%

Chemical Control of Valence Tautomerism of Nickel(II) Semiquinone and Nickel(III) Catecholate States

Ohtsu

Tanaka

2004

Angew Chem Int Ed

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Transition-metal complexes with dioxolene ligands have been attracting much attention because of their characteristic ligand-localized redox reactions among the three redox states of quinone (Q), semiquinone (SQ), and catecholate (Cat) in addition to metal-centered redox reactions.[1] Interest has especially been paid to interconversion of valence tautomers in the metal-dioxolene framework.[1] Valence tautomers are characterized by displacement of electron density to one redox center or the other, for example, M

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A square-planar nickel(III) complex of an innocent ligand system

Cited by 100 publications

References 1 publication

Homoleptic Organoderivatives of High‐Valent Nickel(III)

Homoleptic Organoderivatives of High‐Valent Nickel(III)

Electronic Structural Changes between Nickel(II)–Semiquinonato and Nickel(III)–Catecholato States Driven by Chemical and Physical Perturbation

Chemical Control of Valence Tautomerism of Nickel(II) Semiquinone and Nickel(III) Catecholate States

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