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Fully Reduced and Mixed-Valent Multi-Copper Aggregates Supported by Tetradentate Diamino Bis(thiolate) Ligands.

ABSTRACT: Tetradentate diamino bis(thiolate) ligands (l-N₂S₂(2-)) with saturated linkages between heteroatoms support fully reduced [(Cu(l-N₂S₂))₂Cu₂] complexes that bear relevance as an entry point toward molecules featuring the Cu₂^ICu₂^II(μ₄-S) core composition of nitrous oxide reductase (N₂OR). Tetracopper [(Cu(l-N₂(S^Me₂)₂))₂Cu₂] (l-N₂(S^Me₂H)₂ = N¹,N²-bis(2-methyl-2-mercaptopropane)-N¹,N²-dimethylethane-1,2-diamine) does not support clean S atom oxidative addition but undergoes Cl atom transfer from PhICl₂ or Ph₃CCl to afford [(Cu(l-N₂(S^Me₂)₂))₃(CuCl)₅], 14. When introduced to Cu(I) sources, the l-N₂(S^ArH)₂ ligand (l-N₂(S^ArH)₂ = N¹,N²-bis(2-mercaptophenyl)-N¹,N²-dimethylethane-1,2-diamine), made by a newly devised route from N¹,N²-bis(2-fluorophenyl)-N¹,N²-dimethylethane-1,2-diamine, ultimately yields the mixed-valent pentacopper [(Cu(l-N₂S^Ar₂))₃Cu₂] (19), which has 3-fold rotational symmetry (D₃) around a Cu₂ axis. The single Cu^II ion of 19 is ensconced within an equatorial l-N₂(S^Ar)₂(2-) ligand, as shown by ¹⁴N coupling in its EPR spectrum. Formation of 19 proceeds from an initial, fully reduced product, [(Cu(l-N₂S^Ar₂))₃Cu₂(Cu(MeCN))] (17), which is C₂ symmetric and exceedingly air-sensitive. While unreactive toward chalcogen donors, 19 supports reversible reduction to the all-cuprous state; generation of [19]^1- and treatment with S atom donors only return 19 because structural adjustments necessary for oxidative addition are noncompetitive with outer-sphere electron transfer. Oxidation of 19 is marked by intense darkening, consistent with greater mixed valency, and by dimerization in the crystalline state to a decacopper species ([20]²⁺) of S₄ symmetry.

SUBMITTER: Wang B

PROVIDER: S-EPMC10302893 | biostudies-literature | 2023 Jun

REPOSITORIES: biostudies-literature

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Fully Reduced and Mixed-Valent Multi-Copper Aggregates Supported by Tetradentate Diamino Bis(thiolate) Ligands.

Wang Bo B Barnes Justin J Ferrara Skylar J SJ Sproules Stephen S Zhang Xiaodong X Mague Joel T JT Donahue James P JP

Inorganic chemistry 20230613 25

Tetradentate diamino bis(thiolate) ligands (l-N2S2(2-)) with saturated linkages between heteroatoms support fully reduced [(Cu(l-N2S2))2Cu2] complexes that bear relevance as an entry point toward molecules featuring the Cu2ICu2II(μ4-S) core composition of nitrous oxide reductase (N2OR). Tetracopper [(Cu(l-N2(SMe2)2))2 ...[more]

PMID: 37310001

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Project description:Cuprous and cupric complexes with the new imidazolyl containing tripodal tetradentate ligands {L(MIm), (1H-imidazol-4-yl)-N,N-bis((pyridin-2-yl)methyl)methanamine, and L(EIm), 2-(1H-imidazol-4-yl)-N,N-bis((pyridin-2-yl)methyl)ethanamine}, have been investigated to probe differences in their chemistry, especially in copper(I)-dioxygen chemistry, compared to that already known for the pyridyl analogue TMPA, tris(2-pyridyl)methyl)amine. Infrared (IR) stretching frequencies obtained from carbon monoxide adducts of [(L(MIm))Cu(I)](+) (1a) and [(L(EIm))Cu(I)](+) (2a) show that the imidazolyl donor is stronger than its pyridyl analogue. Electrochemical data suggest differences in the binding constant of Cu(II) to L(EIm) compared to TMPA and L(MIm), reflecting geometric changes. Oxygenation of [(L(MIm))Cu(I)](+) (1a) in 2-methyltetrahydrofuran (MeTHF) solvent at -128 degrees C leads to an intensely purple colored species with a UV-vis spectrum characteristic of an end-on bound peroxodicopper(II) complex [{(L(MIm))Cu(II)}(2)(mu-1,2-O(2)(2-))](2+) (1b(P)) {lambda(max) = 528 nm}, very similar to the previously well characterized complex [{(TMPA)Cu(II)}(2)(mu-1,2-O(2)(2-))](2+) {lambda(max) = 520 nm (epsilon = 12 000 M(-1) cm(-1)), in MeTHF; resonance Raman (rR) spectroscopy: nu(O-O) = 832 (Delta((18)O(2)) = -44) cm(-1)}. In the low-temperature oxygenation of 2a, benchtop (-128 degrees C) and stopped-flow (-90 degrees C) experiments reveal the formation of an initial superoxo-Cu(II) species [(L(EIm))Cu(II)(O(2)(*-))](+) (2b(S)), lambda(max) = 431 nm in THF) . This converts to the low-temperature stable peroxo complex [{(L(EIm))Cu(II)}(2)(mu-1,2-O(2)(2-))](2+) (2b(P)) {rR spectroscopy: nu(O-O) = 822 (Delta((18)O(2)) = -46) cm(-1)}. Complex 2b(P) possess distinctly reduced Cu-O and O-O stretching frequencies and a red-shifted UV-vis feature {to lambda(max) = 535 nm (epsilon = 11 000 M(-1) cm(-1))} compared to the TMPA analogue due to a distortion from trigonal bipyramidal (TBP) to a square pyramidal ligand field. This distortion is supported by the structural characterization of related ligand-copper(II) complexes: A stable tetramer cluster complex [(mu(2)-L(EIm-))(4)(Cu(II))(4)](4+), obtained from thermal decomposition of 2b(P) (with formation of H(2)O(2)), also exhibits a distorted square pyramidal Cu(II) ion geometry as does the copper(II) complex [(L(EIm))Cu(II)(CH(3)CN)](2+) (2c), characterized by X-ray crystallography and solution electron paramagnetic resonance (EPR) spectroscopy.

Dataset Information

Fully Reduced and Mixed-Valent Multi-Copper Aggregates Supported by Tetradentate Diamino Bis(thiolate) Ligands.

Publications

Fully Reduced and Mixed-Valent Multi-Copper Aggregates Supported by Tetradentate Diamino Bis(thiolate) Ligands.

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