Electrochemistry of transition metal clusters

Lemoine, Paul

doi:10.1016/0010-8545(82)85010-8

Cited by 70 publications

(22 citation statements)

References 81 publications

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“…Intriguingly, the reaction of 3 with 30% H 2 O 2 (10 equiv) and 1 equiv of Et 3 N exhibited O (π* σ ) → Cu LMCT transition at 390 nm in CH 3 CN at −40 °C, which may correspond to the Cu II -OOH intermediate (Figure ). The base Et 3 N has seemingly facilitated the binding of H 2 O 2 with the copper(II) center.…”

Section: Results and Discussionmentioning

confidence: 99%

Benzene Hydroxylation by Bioinspired Copper(II) Complexes: Coordination Geometry versus Reactivity

et al. 2020

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A series of bioinspired copper(II) complexes of N 4 -tripodal and sterically crowded diazepane-based ligands have been investigated as catalysts for functionalization of the aromatic C−H bond. The tripodalligand-based complexes exhibited distorted trigonal-bipyramidal (TBP) geometry (τ, 0.70) around the copper(II) center; however, diazepaneligand-based complexes adopted square-pyramidal (SP) geometry (τ, 0.037). The Cu−N Py bonds (2.003−2.096 Å) are almost identical and shorter than Cu−N amine bonds (2.01−2.148 Å). Also, their Cu−O (Cu− O water , 1.988 Å; Cu−O triflate , 2.33 Å) bond distances are slightly varied. All of the complexes exhibited Cu 2+ → Cu + redox couples in acetonitrile, where the redox potentials of TBP-based complexes (−0.251 to −0.383 V) are higher than those of SP-based complexes (−0.450 to −0.527 V). The d−d bands around 582−757 nm and axial patterns of electron paramagnetic resonance spectra [g ∥ , 2.200−2.251; A ∥ , (146−166) × 10 −4 cm −1 ] of the complexes suggest the existence of five-coordination geometry. The bonding parameters showed K ∥ > K ⊥ for all complexes, corresponding to out-ofplane π bonding. The complexes catalyzed direct hydroxylation of benzene using 30% H 2 O 2 and afforded phenol exclusively. The complexes with TBP geometry exhibited the highest amount of phenol formation (37%) with selectivity (98%) superior to that of diazepane-based complexes (29%), which preferred to adopt SP-based geometry. Hydroxylation of benzene likely proceeded via a Cu II -OOH key intermediate, and its formation has been established by electrospray ionization mass spectrometry, vibrational, and electronic spectra. Their formation constants have been calculated as (2.54−11.85) × 10 −2 s −1 from the appearance of an O (π* σ ) → Cu ligand-to-metal charge-transfer transition around 370−390 nm. The kinetic isotope effect (KIE) experiments showed values of 0.97−1.12 for all complexes, which further supports the crucial role of Cu-OOH in catalysis. The 18 O-labeling studies using H 2 18 O 2 showed a 92% incorporation of 18 O into phenol, which confirms H 2 O 2 as the key oxygen supplier. Overall, the coordination geometry of the complexes strongly influenced the catalytic efficiencies. The geometry of one of the Cu II -OOH intermediates has been optimized by the density functional theory method, and its calculated electronic and vibrational spectra are almost similar to the experimentally observed values.

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Section: Results and Discussionmentioning

confidence: 99%

Benzene Hydroxylation by Bioinspired Copper(II) Complexes: Coordination Geometry versus Reactivity

et al. 2020

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“…7, 11 There is a more general interest in the redox chemistry and magnetism of transition metal clusters, and a number of examples have been reported of cluster species that support sequential redox events and/or show paramagnetism in isolated species. [12][13][14][15][16][17] For example [W 6 CCl 18 ] n-(n = 0 to 4), 18 [W 6 NCl 18 ] n-(n = 1 to 3), 19 [FeS 8 (PEt 3 ) 6 ] n+ (n = 0 to 4) 20 and [Mo 6 S 8 (PEt 3 ) 6 ] n (n = 1+ to 2-) 21 have been described; while the hexanuclear cluster compounds with edge bridged halide ligands also exhibit extensive redox behaviour, 22-24 and redox pairs such as [Ta 6 Cl 14 (PEt 3 ) 4 ] n+ (n = 0, 1) have been isolated. 25 Up to ten sequential reversible reductions have been reported for the high-nuclearity platinum cluster [Pt 26 (CO) 32 ] n (n = 0 to -10).…”

Section: Introductionmentioning

confidence: 99%

“…dihedral angle C ipso -P-Rh-Rh ~170 • which reduces the symmetry of the Rh 6 cluster to C 1 . Calculations have indicated that the 12 hydride ligands in H-[12]…”

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confidence: 99%

Using EPR to follow reversible dihydrogen addition to paramagnetic clusters of high hydride count: [Rh₆(PCy₃)₆H₁₂]⁺and [Rh₆(PCy₃)₆H₁₄]⁺

et al. 2010

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A combined structural/EPR/computational chemistry investigation is reported on the two paramagnetic hydrido-cluster salts [Rh 6 4 ] EPR measurements indicate two isomers, the proportion of which change with temperature and deuteration-one axial isomer and one rhombic isomer. DFT calculations on a number of plausible isomers give EPR parameters which fit the experimentally determined rhombic isomer to one in which there is an interstitial hydride in the cluster and thirteen hydride ligands on the surface, while the axial isomer has two dihydrogen-like ligands on the cluster surface. That these isomers lie close in energy comes from both the EPR measurements (as measured from equilibrium constants over a variable temperature range) and DFT calculations. Deuteration of the hydrides should favour the isomer with the lowest zero-point energy and this is the case, with the axial isomer (two D 2 ligands on the surface) being favoured over the rhombic.

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“…However, a combination of electrochemical and spectroscopic research methods makes it possible to study the pathways of the redox reactions of complexes and clusters and determines the products of their electrochemical transformations [26,27]. It is well-known that the electrochemical reactions of polymetallic compounds can be either reversible or irreversible (in which case the metal cores undergo transformations) [28][29][30][31][32]. Moreover, their electrochemical properties and oxidation mechanisms depend on their composition and structure.…”

Section: Introductionmentioning

confidence: 99%

Electrochemically induced transformations of bi- and trinuclear heterometallic vinylidene complexes containing Re, Pd and Fe

Burmakina

Verpekin

Maksimov

et al. 2017

Inorganica Chimica Acta

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Redox-induced transformations of bi-(Cp(CO) 2 RePd(μ-C=CHPh)(PPh 3) 2 (2), Cp(CO) 2 RePd(μ-C=CHPh)(P-P) [P-P =  2-Ph 2 P(CH 2) 2 PPh 2 (dppe) (3),  2-Ph 2 P(CH 2) 3 PPh 2 (dppp) (4)], Cp(CO) 2 ReFe(μ-C=CHPh)(CO) 4 (5) and trinuclear (Cp(CO) 2 ReFe 2 (μ 3-C=CHPh)(CO) 6 (6), CpReFePd(µ 3-C=CHPh)(CO) 5 (P-P) [P-P = dppe (7), dppp (8)] heterometallic vinylidene complexes derived from Cp(CO) 2 Re=C=CHPh (1) were investigated by electrochemical methods. The oxidation processes of clusters 7 and 8 were studied by EPR spectroscopy. The electrochemical properties of clusters 7 and 8 were shown to depend on the nature of the chelate diphosphine ligand at the palladium center in contrast to complexes 3 and 4. The oxidation of complexes 2-4 was found to result in the Re-Pd, Pd-С 1 bond cleavage and formation of rhenium complex 1 and Pd-containing fragments. The oxidation of 7 and 8 resulted in the formation of the radical cations 7 +• and 8 +• , which gradually transformed into a number of intermediate products: Cp(CO) 2 RePd(μ-C=CHPh)(P-P), [Fe(CO) 3 ] +• , [CpReFe 2 (µ 3-C=CHPh)(CO) 6 ] +• and others. The final products of their oxidation in both cases were triangular clusters (CO) 8 Fe 2 Pd(P-P) [P-P = dppe (9), dppp (10)] and rhenium complex 1. The molecular structure of cluster 7 was established by X-ray diffraction analysis.

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Electrochemistry of transition metal clusters

Cited by 70 publications

References 81 publications

Benzene Hydroxylation by Bioinspired Copper(II) Complexes: Coordination Geometry versus Reactivity

Benzene Hydroxylation by Bioinspired Copper(II) Complexes: Coordination Geometry versus Reactivity

Using EPR to follow reversible dihydrogen addition to paramagnetic clusters of high hydride count: [Rh₆(PCy₃)₆H₁₂]⁺and [Rh₆(PCy₃)₆H₁₄]⁺

Electrochemically induced transformations of bi- and trinuclear heterometallic vinylidene complexes containing Re, Pd and Fe

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Electrochemistry of transition metal clusters

Cited by 70 publications

References 81 publications

Benzene Hydroxylation by Bioinspired Copper(II) Complexes: Coordination Geometry versus Reactivity

Benzene Hydroxylation by Bioinspired Copper(II) Complexes: Coordination Geometry versus Reactivity

Using EPR to follow reversible dihydrogen addition to paramagnetic clusters of high hydride count: [Rh6(PCy3)6H12]+and [Rh6(PCy3)6H14]+

Electrochemically induced transformations of bi- and trinuclear heterometallic vinylidene complexes containing Re, Pd and Fe

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Using EPR to follow reversible dihydrogen addition to paramagnetic clusters of high hydride count: [Rh₆(PCy₃)₆H₁₂]⁺and [Rh₆(PCy₃)₆H₁₄]⁺