Controlled nitrene transfer from a tyrosinase-like arylnitroso-copper complex

The reaction between p-nitrosonitrobenzene and the tetramethylpropylenediamine-copper(i) complex yields a dinuclear complex that is structurally and electronically similar to side-on peroxo species known in Cu/O2 chemistry. The complex reacts with di-tert-butylphenolate via nitrene transfer, as observed through an intermediate and the aminophenol product obtained upon reductive work-up

Supramolecular control of monooxygenase reactivity in a copper( ii ) cryptate

International audienc

Redox noninnocence of the bridge in copper(II) salophen and bis(oxamato) complexes

Two square-planar copper(II) complexes of 1,2-bis(2-hydroxy-3,5-di-tert-butylbenzimino)-4,5-bis(dimethylamino)benzene (1) and N-[4,5-bis(dimethylamino)-2-(oxalylamino)benzene]oxamate (22-) were prepared. The crystal structures of the proligands H2L1 and Et2H2L2, as well as the corresponding complexes, are reported. The proligands each display a one-electron-oxidation wave, which is assigned to oxidation of the bis(dimethylamino)benzene moiety into a π radical. Complexes 1 and 22- exhibit reversible one-electron-oxidation waves in their cyclic voltammograms (E1/21 = 0.14 and E1/22 = 0.31 V for 1 and E1/21 = -0.47 V vs Fc+/Fc for 22-). The first process corresponds to oxidation of the bis(dimethylamino)benzene central ring into a π radical, while the second process for 1 is ascribed to oxidation of the π radical into an α-diiminoquinone. The one-electron-oxidized species 1+ and 2- exhibit intense visible-near-IR absorptions, which are diagnostic of π radicals. They display a triplet signal in their electron paramagnetic resonance spectra, which stem from magnetic coupling between the ligand-radical spin and the copper(II) spin. The zero-field-splitting parameters are larger for 2- than 1+ because of greater delocalization of the spin density onto the coordinated amidato N atoms. Density functional theory calculations support a π-radical nature of the one-electron-oxidized complexes, as well as S = 1 ground spin states. The electrogenerated 12+ comprises a closed-shell diiminoquinone ligand coordinated to a copper(II) metal center. Both 1 and 2 catalyze the aerobic oxidation of benzyl alcohol, albeit with different yields

Reversible double oxidation and protonation of the non-innocent bridge in a nickel(II) salophen complex

Substitution on the aromatic bridge of a nickel(II) salophen complex with electron-donating dimethylamino substituents creates a ligand with three stable, easily and reversibly accessible oxidation states. The one-electron-oxidized product is characterized as a nickel(II) radical complex with the radical bore by the central substituted aromatic ring, in contrast to other nickel(II) salen or salophen complexes that oxidize on the phenolate moieties. The doubly oxidized product, a singlet species, is best described as having an iminobenzoquinone bridge with a vinylogous distribution of bond lengths between the dimethylamino substituents. Protonation of the dimethylamino substituents inhibits these redox processes on the time scale of cyclovoltammetry, but electrolysis and chemical oxidation are consistent with deprotonation occurring concomitantly with electron transfer to yield the mono- and dioxidized species described above

Fast palladium catalyzed arylation of alkenes using bulky monodentate phophorous ligands

[EN] The new bimetallic nickel(II) compound (PPh4)4[Ni2(2)]·6H2O (3), where H8[2] stands for N,N',N'',N'''-1,2,4,5-benzene-tetrayltetrakis(oxamic acid), has been synthesized and its crystal structure determined by single-crystal X-ray diffraction. The structure of 3 consists of [Ni2(n4:n4-2)]4- anions, tetraphenylphosphonium cations, and water molecules. Facile one-electron oxidation of the square-planar diamagnetic dinickel(II) complex [Ni2(n4:n4-2)]4- generates the metallo-radical species [Ni2(n4:n4-2·+)]3- with characteristic intra-ligand ¿cation radical transitions in the visible region (475-550 nm) as well as a typical quasi-isotropic EPR signal at g ¿ 2.0.This work was supported by the CNRS (France) and the DGICYT (Spain) through project PB9421002. B. Cervera thanks the Conselleria de Educació i Ciència de la Generalitat Valenciana (Spain) for a grant.Aukauloo, A.; Ottenwaelder, X.; Ruiz, R.; Poussereau, S.; Pei, Y.; Journaux, Y.; Fleurat, P.... (1999). A Square-Planar Dinickel(II) Complex with a Noninnocent Dinucleating Oxamate Ligand: Evidence for a Ligand Radical Species. European Journal of Inorganic Chemistry. 1999(7):1067-1071. https://doi.org/10.1002/(SICI)1099-0682(199907)1999:73.0.CO;2-7S1067107119997Stubbe, J., & van der Donk, W. A. (1998). Protein Radicals in Enzyme Catalysis. Chemical Reviews, 98(2), 705-762. doi:10.1021/cr9400875Sono, M., Roach, M. P., Coulter, E. D., & Dawson, J. H. (1996). Heme-Containing Oxygenases. Chemical Reviews, 96(7), 2841-2888. doi:10.1021/cr9500500Que, L., & Ho, R. Y. N. (1996). Dioxygen Activation by Enzymes with Mononuclear Non-Heme Iron Active Sites. Chemical Reviews, 96(7), 2607-2624. doi:10.1021/cr960039fRecent reviews: [2a] , Chem. Commun. 1998, 1319–1325, and references therein.2b – , , New J. Chem. 1998, 201–210.Wang, Y. (1998). Catalytic Galactose Oxidase Models: Biomimetic Cu(II)-Phenoxyl-Radical Reactivity. Science, 279(5350), 537-540. doi:10.1126/science.279.5350.537Cox, D. D., & Que, L. (1988). Functional models for catechol 1,2-dioxygenase. The role of the iron(III) center. Journal of the American Chemical Society, 110(24), 8085-8092. doi:10.1021/ja00232a021Jang, H. G., Cox, D. D., & Que, L. (1991). A highly reactive functional model for the catechol dioxygenases. Structure and properties of [Fe(TPA)DBC]BPh4. Journal of the American Chemical Society, 113(24), 9200-9204. doi:10.1021/ja00024a028Koch, W. O., & Krüger, H.-J. (1995). Ein sehr reaktives und katalytisch wirksames Modellsystem für intradiolspaltende Catechol-Dioxygenasen: Struktur und Reaktivität von Eisen(III)-Catecholatkomplexen vonN,N′-Dimethyl-2,11-diaza[3.3](2,6)pyridinophan. Angewandte Chemie, 107(23-24), 2928-2931. doi:10.1002/ange.19951072335Inoue, K., & Iwamura, H. (1994). Ferro- and Ferrimagnetic Ordering in a Two-Dimensional Network Formed by Manganese(II) and 1,3,5-Tris[p-(N-tert-butyl-N-oxyamino)phenyl]benzene. Journal of the American Chemical Society, 116(7), 3173-3174. doi:10.1021/ja00086a077MANRIQUEZ, J. M., YEE, G. T., MCLEAN, R. S., EPSTEIN, A. J., & MILLER, J. S. (1991). A Room-Temperature Molecular/Organic-Based Magnet. Science, 252(5011), 1415-1417. doi:10.1126/science.252.5011.1415Zhang, J., Ensling, J., Ksenofontov, V., Gütlich, P., Epstein, A. J., & Miller, J. S. (1998). Molekulare Magnete mitTc-Werten über 100 K und Koerzitivfeldern bis zu 6500 Oe: Synthesen von [MII(tcne)2]⋅x CH2Cl2 (M = Mn, Fe, Co, Ni). Angewandte Chemie, 110(5), 676-679. doi:10.1002/(sici)1521-3757(19980302)110:53.0.co;2-xZhang, J., Ensling, J., Ksenofontov, V., Gütlich, P., Epstein, A. J., & Miller, J. S. (1998). [MII(tcne)2]⋅x CH2Cl2 (M=Mn, Fe, Co, Ni) Molecule-Based Magnets withTc Values Above 100 K and Coercive Fields up to 6500 Oe. Angewandte Chemie International Edition, 37(5), 657-660. doi:10.1002/(sici)1521-3773(19980316)37:53.0.co;2-lCollins, T. J., Powell, R. D., Slebodnick, C., & Uffelman, E. S. (1991). Stable highly oxidizing cobalt complexes of macrocyclic ligands. Journal of the American Chemical Society, 113(22), 8419-8425. doi:10.1021/ja00022a033Bartos, M. J., Kidwell, C., Kauffmann, K. E., Gordon-Wylie, S. W., Collins, T. J., Clark, G. C., … Weintraub, S. T. (1995). Ein stabiler Aquaeisen(III)-Komplex mitS = 1: Struktur und spektroskopische Eigenschaften. Angewandte Chemie, 107(11), 1345-1348. doi:10.1002/ange.19951071121Bartos, M. J., Kidwell, C., Kauffmann, K. E., Gordon-Wylie, S. W., Collins, T. J., Clark, G. C., … Weintraub, S. T. (1995). A Stable Aquairon(III) Complex withS= 1: Structure and Spectroscopic Properties. Angewandte Chemie International Edition in English, 34(11), 1216-1219. doi:10.1002/anie.199512161[8a] , , , , , , , , Chem. Commun. 1998, 989–990.8b – , , , , , , , , Chem. Commun. 1997, 2283–2284.Estrada, J., Fernández, I., Pedro, J., Ottenwaelder, X., Ruiz, R., & Journaux, Y. (1997). Aerobic epoxidation of olefins catalysed by square-planar cobalt(III) complexes of bis-N,N′-disubstituted oxamides and related ligands. Tetrahedron Letters, 38(13), 2377-2380. doi:10.1016/s0040-4039(97)00354-7Fernández, I., Pedro, J., Rosello, A. L., Ruiz, R., Ottenwaelder, X., & Journaux, Y. (1998). Aerobic epoxidation of olefins catalysed by square-planar nickel(II) complexes of bis- N , N ′-disubstituted oxamides and related ligands. Tetrahedron Letters, 39(18), 2869-2872. doi:10.1016/s0040-4039(98)00321-9[10a] , , , , , , J. Chem. Soc., Dalton Trans. 1997, 745–751.10b – , , , , , , , , , , , J. Chem. Soc., Dalton Trans. 1998, 781–790., , , , , , manuscript in preparation.Bossu, F. P., & Margerum, D. W. (1976). The stabilization of trivalent nickel in deprotonated-peptide complexes. Journal of the American Chemical Society, 98(13), 4003-4004. doi:10.1021/ja00429a047Bossu, F. P., Chellappa, K. L., & Margerum, D. W. (1977). Ligand effects on the thermodynamic stabilization of copper(III)-peptide complexes. Journal of the American Chemical Society, 99(7), 2195-2203. doi:10.1021/ja00449a028Fabbrizzi, L., Perotti, A., & Poggi, A. (1983). The deprotonated amido vs. the amino group in the stabilization of coordinated trivalent copper and nickel cations. An electrochemical evaluation. Inorganic Chemistry, 22(9), 1411-1412. doi:10.1021/ic00151a035Anson, F. C., Collins, T. J., Richmond, T. G., Santarsiero, B. D., Toth, J. E., & Treco, B. G. R. T. (1987). Highly stabilized copper(III) complexes. Journal of the American Chemical Society, 109(10), 2974-2979. doi:10.1021/ja00244a020Collins, T. J., Nichols, T. R., & Uffelman, E. S. (1991). A square-planar nickel(III) complex of an innocent ligand system. Journal of the American Chemical Society, 113(12), 4708-4709. doi:10.1021/ja00012a064Hanss, J., & Krüger, H.-J. (1996). Der erste stabile Kupfer(III)-Komplex mit aliphatischen Thiolaten als Liganden: struktureller und spektroskopischer Nachweis von CuII- und CuIII-Ionen in Komplexen mit quadratisch-planaren CuN2S2-Koordinationssphären. Angewandte Chemie, 108(23-24), 2989-2991. doi:10.1002/ange.19961082323Hanss, J., & Krüger, H.-J. (1996). The First Stable Copper(III) Complex Containing Aliphatic Thiolates as Ligands: Structural and Spectroscopic Evidence for CuII and CuIII Ions in Complexes with Square-Planar CuN2S2 Coordination Environments. Angewandte Chemie International Edition in English, 35(2324), 2827-2830. doi:10.1002/anie.199628271Hanss, J., & Krüger, H.-J. (1998). Erste Isolierung und strukturelle Charakterisierung eines Nickel(III)-Komplexes mit aliphatischen Thiolatdonoren. Angewandte Chemie, 110(3), 366-369. doi:10.1002/(sici)1521-3757(19980202)110:33.0.co;2-fHanss, J., & Krüger, H.-J. (1998). First Isolation and Structural Characterization of a Nickel(III) Complex Containing Aliphatic Thiolate Donors. Angewandte Chemie International Edition, 37(3), 360-363. doi:10.1002/(sici)1521-3773(19980216)37:33.0.co;2-pMichaelis, L., Schubert, M. P., & Granick, S. (1939). The Free Radicals of the Type of Wurster’s Salts. Journal of the American Chemical Society, 61(8), 1981-1992. doi:10.1021/ja01877a013Becke, A. D. (1993). Density‐functional thermochemistry. III. The role of exact exchange. The Journal of Chemical Physics, 98(7), 5648-5652. doi:10.1063/1.464913Lee, C., Yang, W., & Parr, R. G. (1988). Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. Physical Review B, 37(2), 785-789. doi:10.1103/physrevb.37.785, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Gaussian 94, Revision E. 1, Gaussian, Inc., Pittsburgh, PA, 1995. In the calculations, the metal ions and the ligand have been explicitly taken into account. The PPh4+ counterions have been replaced by Na+ cations and are located at the phosphorus site of PPh4+ cations. Furthermore, the geometry used has been taken from the one determined by X-ray crystallography. We have used the 6–31G* basis set for the ligands atoms. The nickel basis set is that determined by Wachters supplemented with f-polarization function. The sodium cations have been taken as point charges (no vacant orbital on the atom), the core electrons being described by an effective core potential. This procedure, which explicitly takes into account a repulsion potential, avoids too strong orbital polarizations towards the point charges.Wachters, A. J. H. (1970). Gaussian Basis Set for Molecular Wavefunctions Containing Third‐Row Atoms. The Journal of Chemical Physics, 52(3), 1033-1036. doi:10.1063/1.1673095Gordon-Wylie, S. W., Claus, B. L., Horwitz, C. P., Leychkis, Y., Workman, J. M., Marzec, A. J., … Collins, T. J. (1998). 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Long-Range Magnetic Coupling through Extended p-Conjugated Aromatic Bridges in Dinuclear Copper(II) Metallacyclophanes

[EN] Self-assembly of 1,4-phenylenebis(oxamate) and 4,4`-biphenylenebis(oxamate) ligands and Cu2+ ions gives two new dinuclear copper(II) metallacyclophanes where the two metal centers are connected by double para-substituted aromatic diamide bridges. Despite the relatively large intramolecular Cu¿Cu distance of ca. 8 and 12 Å for each complex, magnetic susceptibility measurements evidence strong to moderately strong intramolecular antiferromagnetic couplings (¿J values of the order of 100 and 10 cm-1, respectively). Density functional theory calculations on these compounds and their homologues with linear oligo-p-phenylenediamide bridges predict a rather slow exponential decay of magnetic coupling with increasing intermetal distance (r values up to 25 Å) along this novel series of dicopper metalla-amidocyclophanes.This work was supported by the Ministerio de Ciencia y Tecnología (Spain) through the Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica (Projects BQU2001-2928 and BQU2001-3017) and the Ramón y Cajal program. Further support from the TMR program of the European Union (Contract ERBFM-RXCT980181) is acknowledged. E.P. thanks the Ministerio de Educación, Cultura y Deporte (Spain) for a grant.Pardo, E.; Faus, J.; Julve, M.; Lloret, F.; Muñoz Roca, MDC.; Cano, J.; Ottenwaelder, X.... (2003). Long-Range Magnetic Coupling through Extended p-Conjugated Aromatic Bridges in Dinuclear Copper(II) Metallacyclophanes. Journal of the American Chemical Society. 125(36):10770-10771. https://doi.org/10.1021/ja030060fS10770107711253

Targeted ferromagnetic coupling in a trinuclear copper(II) complex: Analysis of the S-t-3/2 spin ground state

Glaser T, Heidemeier M, Grimme S, Bill E. Targeted ferromagnetic coupling in a trinuclear copper(II) complex: Analysis of the S-t-3/2 spin ground state. Inorganic Chemistry. 2004;43(17):5192-5194.The trinuclear Cu-II complex [(talen)Cu(II)3] (1) using the new triplesalen ligand H(6)talen has been synthesized and structurally characterized. The three Cull ions are bridged in a m-phenylene linkage by the phloroglucinol backbone of the ligand. This m-phenylene bridging mode results in ferromagnetic couplings with an S-t = 3/2 spin ground state, which has been analyzed by means of EPR spectroscopy and DFT calculations. The EPR spectrum exhibits an unprecedented pattern of 10 hyperfine lines due to the coupling of three Cull ions (I = 3/2). Resonances around g = 4 in both perpendicular and parallel mode EPR spectra demonstrate a zero-field splitting of D similar to 74 x 10(-4) cm(-1) arising from an isotropic/antisymmetric exchange interactions. The DFT calculations show an alteration in the sign of the spin densities of the central benzene ring corroborating the spin-polarization mechanism as origin for the ferromagnetic coupling