Preparation, Magnetism, and Crystal Structures of the Tautomers [LCu(μ2‐OH)2CuL](ClO4)2 (Blue) and [LCu(μ2‐OH2)(μ2‐O)CuL](ClOμ4)μ2 (Green): μ‐Aqua‐μ‐oxo vs. Di‐μ‐hydroxo Linkage

Chaudhuri, Phalguni; Ventur, D.; Wieghardt, Karl; Peters, Е.-М.; Peters, Karl; Simon, Arndt

doi:10.1002/anie.198500571

Cited by 66 publications

(29 citation statements)

References 6 publications

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“…This related complex also shows a distorted square pyramidal coordination sphere around the Cu atoms and two hydroxo bridges with similar Cu-O distances [1.964 (4) and 1.893 (5) Å] to those in the present structure [1.904 (2) and 1.988 (2) Å]. This bonding situation seems to be common in this type of Cu II complex and was also observed in the hydroxo-bridged cyclic triamine Cu II compoounds N,N′,N′′-trimethyl-1,4,7-triazacyclononane [Cu-O 1.936 (4) and 1.939 (4) Å] (Chaudhuri et al, 1985), N-4-but-1-ene-1,4,7-triazacyclononane [Cu-O 1.929 (2) Å; Farrugia et al, 1996] and other triazacyclononane complexes with different substitution patterns (Mahapatra et al, 1996). A special feature of the title compound is its distortion of the square-…”

Section: Data Collectionsupporting

confidence: 78%

A centrosymmetric hydroxo-bridged pentamethyldiethylenetriamine copper(II) complex, {[(pmdeta)Cu(OH)]₂}²⁺·2Br⁻·2MeCN

Kickelbick

2001

Acta Cryst E

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Section: Data Collectionsupporting

confidence: 78%

A centrosymmetric hydroxo-bridged pentamethyldiethylenetriamine copper(II) complex, {[(pmdeta)Cu(OH)]₂}²⁺·2Br⁻·2MeCN

Kickelbick

2001

Acta Cryst E

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“…This single ligand was identified as an oxo ligand by comparing the interatomic distance with bond lengths determined within Cu II (m-OH) 2 Figure 4, Me 3 tacn = N,N',N''-trimethyl-1,4,7-triazacyclononane) starting however, with copper(II) precursors. [46] The green maqua-m-oxo complex 17 was shown to transform into its blue tautomer [(Me 3 tacnCu II ) 2 (m-OH) 2 ](ClO 4 ) 2 (18) in the presence of traces of water underlining the high sensitivity of Cu 2 O complexes to water. Also the determination of the molecular structures of the two different-colored compounds with the aid of single-crystal X-ray diffraction was reported.…”

Section: Copper Oxo Complexesmentioning

confidence: 99%

Molecular Cu^II‐O‐Cu^II Complexes: Still Waters Run Deep

Haack

Limberg

2014

Angew Chem Int Ed

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Research on O2 activation at ligated Cu(I) is fueled by its biological relevance and the quest for efficient oxidation catalysts. A rarely observed reaction is the formation of a Cu(II) -O-Cu(II) species, which is more special than it appears at first sight: a single oxo ligand between two Cu(II) centers experiences considerable electron density, and this makes the corresponding complexes reactive and difficult to access. Hence, only a small number of these compounds have been synthesized and characterized unequivocally to date, and as biological relevance was not apparent, they remained unappreciated. However, recently they moved into the spotlight, when Cu(II) -O-Cu(II) cores were proposed as the active species in the challenging oxidation of methane to methanol at the surface of a Cu-grafted zeolite and in the active center of the copper enzyme particulate methane monooxygenase. This Minireview provides an overview of these systems with a special focus on their reactivity and spectroscopic features.

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“…In addition, an ESI mass spectrum of the final reaction solution revealed the presence of {[L 2 Cu 2 (OH) 2 ]SbF 6 } + (calc. m/z 739.1048, found 739.0960) 19,20. Peaks corresponding to this product are not present in the spectrum of the solution resulting from decay of 1a in the absence of N 2 O.…”

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confidence: 94%

Reduction of Nitrous Oxide to Dinitrogen by a Mixed Valent Tricopper-Disulfido Cluster

et al. 2009

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The greenhouse gas N 2 O is converted to N 2 by a µ-sulfido-tetracopper active site in the enzyme nitrous oxide reductase (N 2 OR) via a process postulated to involve µ-1,3 coordination of N 2 O to two Cu(I) ions. In efforts to develop synthetic models of the site with which to test mechanistic hypotheses, we have prepared a localized mixed valent Cu(II)Cu(I) 2 cluster bridged in µ-η 2 :η 1 :η 1 fashion by disulfide, [L 3 Cu 3 (µ 3 -S 2 )]X 2 (L = 1,4,7-trimethyl-triazacyclononane, X = O 3 SCF 3 − or SbF 6 − ). This cluster exhibits spectroscopic features similar to those of the active site in N 2 OR and reacts with N 2 O to yield N 2 in a reaction that models the function of the enzyme. Computations implicate a transition state structure that features µ-1,1-bridging of N 2 O via its O-atom to a [L 2 Cu 2 (µ-S 2 )] + fragment and provide chemical precedence for an alternative pathway for N 2 O reduction by N 2 OR.Nitrous oxide (N 2 O) is an important greenhouse gas and component of the global nitrogen cycle. 1 Its reduction to dinitrogen (N 2 ) is thermodynamically favorable (E° = 1.76 V), making it attractive as an environmentally benign oxidant, yet its utility in this regard is limited by high kinetic barriers that limit reaction rates. Transition metals facilitate the reduction of N 2 O, although in most heterogeneous catalytic systems high temperatures are required 2 and homogeneous processes that operate under mild conditions generally use highly reducing lowvalent metal complexes. [3][4][5] In Nature, conversion of N 2 O to N 2 and H 2 O is catalyzed under ambient conditions during microbial dentrification by the metalloenzyme nitrous oxide reductase, N 2 OR. 6 X-ray crystallographic, 7 spectroscopic, and theoretical studies 8 have identified the active site of N 2 OR as a µ-sulfido-tetracopper cluster without precedent in biology or synthetic chemistry, which cycles through tetracopper(I) and mixed-valent states during catalysis. 9 A provocative mechanism for N 2 O reduction has been suggested that involves µ-1,3-coordination and bending of N 2 O between two of the copper ions in the fully reduced (all copper(I)) cluster, with the µ-sulfide acting to facilitate electron delocalization during the redox process. (Figure 1). The structures and spectroscopic properties of these complexes are similar to each other and to those of others with antiferromagnetically coupled (µ-η 2 :η 2 -disulfido)dicopper(II) cores. 11b, 12 For example, they are EPR silent and exhibit an intense S 2 2− → Cu(II) charge transfer transition at ~395 nm (ε 15,000 M −1 cm −1 , Figure 1c, red line), excitation into which (λ ex 406.7 or 457.0 nm) results in resonance enhancement of a peak in the Raman spectrum at ~431 cm −1 (Δ 34 S = 19 cm −1 ) attributable to an S-S stretching mode.Monitoring the reactions by UV-vis spectroscopy revealed the formation and subsequent decay (at room temperature, t 1/2 ~ 45 min) of an intermediate with λ max = 634 (1a) or 631 (1b) nm, respectively, the lifetime of which can be extended significa...

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Preparation, Magnetism, and Crystal Structures of the Tautomers [LCu(μ₂‐OH)₂CuL](ClO₄)₂ (Blue) and [LCu(μ₂‐OH₂)(μ₂‐O)CuL](ClOμ₄)μ₂ (Green): μ‐Aqua‐μ‐oxo vs. Di‐μ‐hydroxo Linkage

Cited by 66 publications

References 6 publications

A centrosymmetric hydroxo-bridged pentamethyldiethylenetriamine copper(II) complex, {[(pmdeta)Cu(OH)]₂}²⁺·2Br⁻·2MeCN

A centrosymmetric hydroxo-bridged pentamethyldiethylenetriamine copper(II) complex, {[(pmdeta)Cu(OH)]₂}²⁺·2Br⁻·2MeCN

Molecular Cu^II‐O‐Cu^II Complexes: Still Waters Run Deep

Reduction of Nitrous Oxide to Dinitrogen by a Mixed Valent Tricopper-Disulfido Cluster

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Preparation, Magnetism, and Crystal Structures of the Tautomers [LCu(μ2‐OH)2CuL](ClO4)2 (Blue) and [LCu(μ2‐OH2)(μ2‐O)CuL](ClOμ4)μ2 (Green): μ‐Aqua‐μ‐oxo vs. Di‐μ‐hydroxo Linkage

Cited by 66 publications

References 6 publications

A centrosymmetric hydroxo-bridged pentamethyldiethylenetriamine copper(II) complex, {[(pmdeta)Cu(OH)]2}2+·2Br−·2MeCN

A centrosymmetric hydroxo-bridged pentamethyldiethylenetriamine copper(II) complex, {[(pmdeta)Cu(OH)]2}2+·2Br−·2MeCN

Molecular CuII‐O‐CuII Complexes: Still Waters Run Deep

Reduction of Nitrous Oxide to Dinitrogen by a Mixed Valent Tricopper-Disulfido Cluster

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Product

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Preparation, Magnetism, and Crystal Structures of the Tautomers [LCu(μ₂‐OH)₂CuL](ClO₄)₂ (Blue) and [LCu(μ₂‐OH₂)(μ₂‐O)CuL](ClOμ₄)μ₂ (Green): μ‐Aqua‐μ‐oxo vs. Di‐μ‐hydroxo Linkage

A centrosymmetric hydroxo-bridged pentamethyldiethylenetriamine copper(II) complex, {[(pmdeta)Cu(OH)]₂}²⁺·2Br⁻·2MeCN

A centrosymmetric hydroxo-bridged pentamethyldiethylenetriamine copper(II) complex, {[(pmdeta)Cu(OH)]₂}²⁺·2Br⁻·2MeCN

Molecular Cu^II‐O‐Cu^II Complexes: Still Waters Run Deep