The reactivity of dicopper(I) complexes of the ligands α,α'-bis(4,7-diisopropyl-1,4,7-triazacyclononan-1-yl)-p- and m-xylene (p- and m-XYLiPr4) with dioxygen was examined by spectroscopic and rapid stopped-flow kinetics methods. Only bis(μ-oxo)dicopper(III) core formation was observed with p-XYLiPr4, but both (μ-η2:η2-peroxo)dicopper(II) and bis(μ-oxo)dicopper(III) species were generated in the m-XYLiPr4 case, their relative proportions being dependent on the solvent, concentration of the dicopper(I) precursor, and temperature. Subsequent decomposition under conditions that favored bis(μ-oxo) core formation resulted in oxidative N-dealkylation of isopropyl groups, whereas μ-η2:η2-peroxo decay led to the product resulting from hydroxylation of the bridging arene, [(m-XYLiPr4-O)Cu2(μ-OH)](SbF6)2. Evidence from kinetics studies, decomposition product analyses, and comparison to the chemistry exhibited by complexes of other substituted 1,4,7-triazacyclonane ligands support a model for the oxygenation of the m-XYLiPr4 compound involving initial, essentially rate-limiting 1:1 Cu:O2 adduct formation followed by partitioning between intra- and intermolecular pathways. At low temperature and high starting material concentrations, the latter route that yields tetranuclear "dimer-of-dimer" species and/or higher order oligomers with bis(μ-oxo) cores is favored, while at higher temperatures and dilution, intramolecular reaction predominates to afford a (peroxo)dicopper(II) species. The course of the subsequent decompositions of these oxygenated products correlates with their proposed formulations. Thus, analysis of final products and kinetics data, including with selectively deuterated compounds, showed that N-dealkylation arises from the high-nuclearity bis(μ-oxo) species and arene hydroxylation occurs upon decay of the intramolecular peroxo complex. Geometric rationales for the divergent oxygenation and decomposition reactions supported by p- and m-XYLiPr4 are proposed.
Copper(I)−dioxygen interactions are of great interest due to their role in biological O2-processing as well as their importance in industrial oxidation processes. We describe here the study of systems which lead to new insights concerning the factors which govern Cu(II)-μ-η2:η2 (side-on) peroxo versus Cu(III)−bis-μ-oxo species formation. Drastic differences in O2-reactivity of Cu(I) complexes which differ only by a single −CH3 versus −H substituent on the central amine of the tridentate ligands employed are observed. [Cu(MeAN)]B(C6F5)4 (1) (MeAN = N,N,N',N',N'-pentamethyl-dipropylenetriamine) reacts with O2 at −80 °C to form almost exclusively the side-on peroxo complex [{CuII(MeAN)}2(O2)]2+ (3) in CH2Cl2, tetrahydrofuran, acetone, and diethyl ether solvents, as characterized by UV−vis and resonance Raman spectroscopies. In sharp contrast, [Cu(AN)]B(C6F5)4 (2) (AN = 3, 3'-iminobis(N,N-dimethyl-propylamine) can support either Cu2O2 structures in a strongly solvent-dependent manner. Extreme behavior is observed in CH2Cl2 solvent, where 1 reacts with O2 giving 3, while 2 forms exclusively the bis-μ-oxo species [{CuIII(AN)}2(O)2]2+ (4Oxo). Stopped-flow kinetics measurements also reveal significant variations in the oxygenation reactions of 1 versus 2, including the observations that 4Oxo forms much faster than does 3; the former decomposes quickly, while the latter is quite stable at 193 K. The solvent-dependence of the bis-μ-oxo versus side-on peroxo preference observed for 2 is opposite to that reported for other known copper(I) complexes; the factors which may be responsible for the unusual behavior of 1/O2 versus 2/O2 (possibly N−H hydrogen bonding in the AN chemistry) are suggested. The factors which affect bis-μ-oxo versus side-on peroxo formation continue to be of interest.
The O 2 -reaction chemistry of 1:1 mixtures of (F 8 )Fe II (1; F 8 = tetrakis(2,6-diflurorophenyl)porphyrinate) and [(L Me 2 N )Cu I ] + (2; L Me 2 N = N , N -bis{2-[2-( N ′, N ′-4-dimethylamino)pyridyl]ethyl}methylamine) is described, to model aspects of the chemistry occurring in cytochrome c oxidase. Spectroscopic investigations, along with stopped-flow kinetics, reveal that low-temperature oxygenation of 1/2 leads to rapid formation of a heme-superoxo species (F 8 )Fe III -(O \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{2}^{-}}}\end{equation*}\end{document} ) (3), whether or not 2 is present. Complex 3 subsequently reacts with 2 to form [(F 8 )Fe III –(O \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{2}^{2-}}}\end{equation*}\end{document} )–Cu II (L Me 2 N )] + (4), which thermally converts to [(F 8 )Fe III –(O)–Cu II (L Me 2 N )] + (5), which has an unusually bent (Fe–O–Cu) bond moiety. Tridentate chelation, compared with tetradentate, is shown to dramatically lower the ν(O–O) values observed in 4 and give rise to the novel structural features in 5.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Phenyl substituents in the 6-positions of terpyridine ligands are important for controlling the spin state of their iron(II) complexes. The introduction of phenyl substituents in both the 6- and 6″-positions leads exclusively to the orange high-spin iron(II) complexes, whilst the presence of a single 6-phenyl substituent results in spin-crossover systems (see scheme).
The kinetic and thermodynamic behavior of O2-binding to Cu(I) complexes can provide fundamental understanding of copper(I)/dioxygen chemistry, which is of interest in chemical and biological systems. Here we report stopped-flow kinetic investigations of the oxygenation reactions of a series of tetradentate copper(I) complexes [(LR)CuI(MeCN)]+ (1R, R = H, Me, tBu, MeO, Me2N) in propionitrile (EtCN), tetrahydrofuran (THF), and acetone. The syntheses of 4-pyridyl substituted tris(2-pyridylmethyl)amine ligands (LR) and copper(I) complexes are detailed. Variations of ligand electronic properties are manifested in the electrochemistry of 1R and ν(CO) of [(LR)CuI−CO]+ complexes. The kinetic studies in EtCN and THF show that the O2-reactions of 1R follow the reaction mechanism established for oxygenation of 1H in EtCN (J. Am. Chem. Soc. 1993, 115, 9506), involving reversible formation (k1/k-1) of [(LR)CuII(O2-)]+ (2R), which further reacts (k2/k-2) with 1R to form the 2:1 Cu2O2 complex [{(LR)CuII}2(O22-)]2+ (3R). In EtCN, the rate constants for formation of 2R (k1) are not dramatically affected by the ligand electronic variations. For R = Me and tBu, the kinetic and thermodynamic parameters are very similar to those of the parent complex (1H); e.g., k1 is in the range 1.2 × 104 to 3.1 × 104 M-1 s-1 at 183 K. With the stronger donors R = MeO and Me2N, more significant effects were observed, with the expected increase in thermodynamic stability of resultant 2R and 3R complexes, and decreased dissociation rates. The modest ligand electronic effects manifested in EtCN are due to the competitive binding of solvent and dioxygen to the copper centers. In THF, a weakly coordinating solvent, the formation rate for 2H is much faster (≥100 times) than that in EtCN, and the thermodynamic stabilities of both the 1:1 (K1) and 2:1 (β = K1K2) copper−dioxygen species are much higher than those in EtCN (e.g., for 2H, ΔH° (K1) = −41 kJ mol-1 in THF versus −29.8 kJ mol-1 in EtCN; for 3H, ΔH° (β) = −94 kJ mol-1 in THF versus −77 kJ mol-1 in EtCN). In addition, a more significant ligand electronic effect is seen for the oxygenation reactions of 1MeO in THF compared to that in EtCN; the thermal stability of superoxo- and peroxocopper complexes are considerably enhanced using LMeO compared to LH. In acetone as solvent, a different reaction mechanism involving dimeric copper(I) species [(LR)2CuI2]2+ is proposed for the oxygenation reactions, supported by kinetic analyses, electrical conductivity measurements, and variable-temperature NMR spectroscopic studies. The present study is the first systematic study investigating both solvent medium and ligand electronic effects in reactions forming copper−dioxygen adducts.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCopper-mediated hydroxylation of an arene: kinetics and mechanism of the reaction of a dicopper(II) m-xylyl-containing complex with H2O2 to yield a phenoxodicopper(II) complexRichard W. Cruse, Susan. Kaderli, Charles J. Meyer, Andreas D. Zuberbuehler, and Kenneth D. KarlinCite this: J. Am. Chem. Soc. 1988, 110, 15, 5020–5024Publication Date (Print):July 1, 1988Publication History Published online1 May 2002Published inissue 1 July 1988https://pubs.acs.org/doi/10.1021/ja00223a020https://doi.org/10.1021/ja00223a020research-articleACS PublicationsRequest reuse permissionsArticle Views431Altmetric-Citations27LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
