Copper dioxygen complexes reactivity

Continuing their efforts with similar ligands, they prepared a thermally sensitive crystal of a bis(/i-qxo)dicopper(II I) compound (3).28 Average Cu O bond distance and Cu-Cu distance are 1.806 A and 2.743 A, respectively. Spectroscopic and kinetic parameters for this compound were also investigated. They also studied the reactivity properties of the copper-dioxygen complexes.25... 

Karlin, K. D. Zuberbuhler, A. D. Formation, structure, and reactivity of copper dioxygen complexes, Bioinorganic Catalysis , 2nd edn. (Revised and Expanded) Eds. Reedijk, J. Bouwman, E. Marcel Dekker New York, 1999, pp. 469-534. Fukuzumi, S. Imahori, H. Biomimetic electron-transfer chemistry of porphyrins and metalloporphyrins, Electron Transfer in Chemistry , Vol. 2 Ed. Balzani, V. Wiley-VCH Verlag GmbH Weinheim, 2001, pp. 927-975. 

Formation, Structure, and Reactivity of Copper Dioxygen Complexes... 

A trans-n- 1,2-Peroxo Dicopper(II) Complex. Our own efforts have resulted in the structural and spectroscopic characterization of five types of copper-dioxygen complexes (6), distinguished on the basis of the ligands used for their synthesis and on their distinctive structures or physical properties. Thus, the manner in which hemocyanin binds 02 is not the only one possible, and it is of considerable interest to deduce the structures, along with associated spectroscopy and reactivity of a variety of types. Dioxygen can bind to dinuclear transition metals in a variety of structural modes, shown in Figure 2. As mentioned, mode C is present in oxy-Hc and Kitajima s model complex (Scheme 1), whereas we have structural and spectroscopic evidence for types A (30-32), B (33-35), and F (36-38) for peroxo 022- binding, and mode D (39, 40) in the case of hydroperoxo (OOH ) complexes. 

K. D. Karlin and A. D. Zuberbuhler, in Formation, Structure and Reactivity of Copper Dioxygen Complexes , ed. J. Reedijk and E. Bouwman, Marcel DekkerNew York, 1999. 

Copper-dioxygen complexes are necessary intermediates in the biomimetic oxidations performed by type 3 Cu models. Several structural motifs for synthetic Cu 02 complexes exist and the main types are shown in Scheme 4. Their mechanism of formation, structural characteristics, spectroscopic and thermodynamic properties, and reactivity have been recently thoroughly reviewed (62,63). In general, the reaction between a Cu(I) complex and dioxygen initially forms a 1 1 Cu/02 adduct that, in the absence of steri-cally hindered ligands, rapidly evolves to the thermodynamically more stable 2 1 Cu/02 adduct. According to the usual formalism, these processes can be described by the following equilibria ... 

Karlin, K.D. Tyeklar, Z. Zuberbiihler, A.D. Formation, Structure, and Reactivity of Copper Dioxygen Complexes. In Bioinorganic Catalysis Reedijk, J.,Ed. Marcel Dekker, Inc. New York, 1993 261-315. 

Biomimetic copper-dioxygen chemistry has advanced considerably since the first structurally-characterized copper-dioxgygen adduct. However, it has been difficult to simulate the room-temperature stability of hemocyanin in these model complexes due to the fact that unlike the enzyme active sites, these models usually do not possess protective environments which can help stabilize potentially reactive copper-dioxygen species. Recently, two room-temperature stable copper-dioxygen complexes have been synthesized which come closer to the goal of mimicking the dioxygen carrier hemocyanin. 

In an elegant approach, Comba and co-workers initiated molecular-mechanics-based models that allow the rational design of ligand systems which are able to stabilize copper-dioxygen compounds. As a part of this investigation, complexes (241) (r = 0.12),223 (242) (r = 0.31),224 and (243) (r = 0.85)224 were synthesized and the reactivity of copper(I) complexes (Section 6.6.4.2.2(iv)) with dioxygen was investigated. 

The reactivity of dioxygen with nitrogen-coordinated copper(I) complexes has received extensive attention over the past two decades [53,54]. To date, analogous reactivity has not been realized for NHC-coordinated Cu(I). Ster-ically unhindered bis-carbene complexes of Cu(I) undergo rapid conversion to the corresponding ureas upon exposure to air in CH2CI2 solution (Eq. 4) [55]. This result suggests NHCs may not be universally applicable to metal-mediated oxidation chemistry. 

Two-electron reduction of dioxygen into coordinated peroxide can be easily performed by two metal centers undergoing concomitant one-electron oxidations, as shown in Equation 4.4 (Section 4.2.2). A variety of transition metal ions (cobalt, nickel, iron, manganese, copper, etc.) can form dinuclear peroxides. These complexes differ in structure (cA-p-1,2-peroxides, trans- l- 1,2-peroxides, p-r 2 r 2-peroxides), in stability and subsequent reactivity modes, and in the protonation state of the peroxo ligands (Figure 4.3). In certain cases, dinuclear p-r 2 r 2-peroxides and bis-p-oxo diamond core complexes interconvert, as discussed below for copper-dioxygen adducts. 

Schindler, S. Reactivity of copper(I) complexes towards dioxygen. Eur. J. Inorg. Chem. 2000, 2311-2326. 

Suzuki, M. Ligand effects on dioxygen activation by copper and nickel complexes reactivity and intermediates. Acc. Chem. Res. 2007, 40, 609-617. 

Reactivity of copper(I) complexes with heterocyclic ligands towards dioxygen 00EJI2311. 

Copper(I) complexes supported by certain capping ligands react with molecular oxygen in a 2 1 ratio to afford dinuclear copper dioxygen (CU2/O2) complexes. Such complexes can be regarded as structural and functional models of the reactive intermediates of tyrosinase and catechol oxidase. Numerous review articles on the subject have been published so far. ... 

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