Copper dioxygen complexes dinuclear

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. 

In contrast to iron and cobalt, end-on superoxo-copper(II) species do not dominate the field of copper-oxygen chemistry. In 1 1 copper-dioxygen adducts, an alternative side-on, t 2 coordination mode is sometimes observed these [(L)Cu11 (t 2-(02 ")] or [(L)Cum-(ri2-(022 )] complexes are discussed below. Mononuclear copper-dioxygen complexes easily react with the second molecule of the Cu(I) complex, forming peroxo- or dioxo-bridged dinuclear species (Section 4.4). For sterically unhindered... 

During the course of modeling copper dioxygen chemistry, Kitajima et al. reported the synthesis of a yu-peroxo dinuclear complex with a 3,5-dimethyl-substituted tris(pyrazolyl)borate ligand, which showed remarkable physicochemical similarities to oxy-Hc and oxy-Tyr. Using a 3,5-di-isopropyl-substituted terminal ligand, they provided the first structural proof of the existence of peroxo dicopper(II) core (108) (copper geometry distorted square pyrami-... 

Figure 9-30. The oxidation of 9.14 by dioxygen and copper(i) generates a dinuclear copper(n) complex of the phenolic ligand 9.15.

A typical example of the more complex reactions that may occur when aromatic compounds react with dioxygen in the presence of copper salts is seen in Fig. 9-30. When solutions of the hexadentate ligand 9.14 react with copper salts and dioxygen, a complex of a new ligand is obtained. The new phenolic compound that is formed acts as a dinucleating ligand and its dinuclear copper(n) complexes turn out to be effective oxygenation catalysts for other substrates. 

In continuing low-temperature kinetic studies of halo-Cu(I)-amine reactions with 02, Davies et al. have observed and partially characterized per-oxo-copper(II) complexes for L2Cu2C12 (L = teed) [96,97]. At room temperature, complete reduction of dioxygen occurs to give green, dinuclear LCu(Cl,0,Cl)CuL, but at lower temperatures (i.e., <-26°C) two forms of a tetra-nuclear mixed-valence peroxo Cu(II) complex exist in equilibrium. In particular, one of the forms is associated with 380 (e = 1600 M l cm-1) and 650 (e = 650) nm electronic spectral absorptions and a resonance Raman Vo 0 band at 822 cm-1. 

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. 

Becker, M., Schindler, S., Karlin, K. D., et al., Intramolecular ligand hydroxylation Mechanistic high-pressure studies on the reaction of a dinuclear copper(I) complex with dioxygen. Inorg. Chem. 1999, 38, 1989-1995. 

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. ... 

Dioxygen binding in a dinuclear copper(I)-complex, based on a macrocyclic tetra Schiff base ligand 11, was reported by Martell and co-workers (scheme 5). 

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