Copper mononuclear species

Nickel atoms have also been allowed to react with C2H4 under cryogenic conditions (101,123). Depending on the metal-concentration conditions and the deposition temperature, either mononuclear species, Ni(C2H4) , n = 1-3(123), or multinuclear species, Ni2(C2H4) ,m = 1-2, and Ni3(CjH4)i, may be isolated. Unlike the copper complexes, these species are all colorless the mononuclear ethylene complexes each dis-... 

The copper atom-acetylene matrix-reaction, monitored originally by esr spectroscopy (60) has now been investigated by IR/UV-visible spectroscopy (144), and there is general agreement on the identification of two mononuclear species, CuCCaHali.. The esr/IR/UV-visible... 

Determination of the catalytically active species derived from 1 in solution. Spectrophotoraetric titration of the backbone ligand 5 with copper(II) acetate in methanol revealed formation of a dinuclear copper(ll) complex species Cu2L.3h(OAc) above a 1 2 molar ratio. A mononuclear copper(ll) species CuL 2h (6) dominates at a 1 1 molar ratio of 5 and copper(ll) acetate. Control experiments for the assignment of putative structures based on the obtained spectroscopic data included a UVA is spectroscopic titration of 5 with anhydrous sodium acetate in the presence of copper(ll) chloride and revealed that acetate is necessary for the formation of a copper (11) complex in methanol. The composition of 1 in methanol is the same as determined by elemental analysis for the sohd state. 

A dinuclear salen complex was investigated as catalyst for the aerobic oxidation of 3,5-di-ferf.-butylcatechol into 3,5-di-teri.-butylquinone in organic and aqueous organic solution. The actual catalyst composition varies in both solvent systems. Formation of a mononuclear species competes with formation of a dinuclear copper(ll) catalyst. The aerobic oxidation of 8 into 9 is 140,000-fold accelerated over background in aqueous methanol, and is about twice as fast as the same reaction in pure methanol. 

Uniquely, the Cu +-neomycin B system has been shown to form two-centered copper complexes at pH values below 6.5 if the metal ion is present in excess (Table 8.3) with less than 15% (relative to total Cu + present) of mononuclear species detected at pH values in the range of 4 to 6. At a 2 1 Cu + neomycin B stoichiometric ratio it was shown that only the dinuclear species exists in solution at pH 7.5. The second binding site in the dinuclear complex was proposed to be in ring D, however, this unique feature is only observed in the case of the copper complex of neomycin B. 

The bis(methylthio)-substituted quarterpyridine, 4, 4"-bis(methylthio)-2,2 6, 2" 6, 2" -quaterpyridine (44), yields a binuclear copper(I) complex, but a mononuclear species with copper(II). ° A spectroelectrochemical study indicated that a redox-induced transformation occurs between these two complex species. The X-ray structure of the 2 2 [copper(I) ligand] helical complex confirmed that each copper is tetrahedrally co-ordinated to four pyridyl nitrogens from two ligand strands, with a short Cu-Cu distance of 3.32 A being present. 

Figure 11. Structure drawing of the mononuclear copper(lI) species [Cu(dcmpz)2(py)2]. 229, containing two unidentate 3,5-dicarbomethoxypyrazolate groups in a trans conformation. [Based on...

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... 

The multicomponent assembly of the tricopper(I) metallostar [(21) Cu(20) 3] (2 from (21), (20) and [Cu(MeCN)4][BF4] in CH2CI2 has been described by Lehn and Baxter. This self-assembly process is the prototype reaction for the construction of a series of heteroleptic multi-nuclear cylindrical species. The related complex [(24) Cu(dppe) 3] has been reported and is of interest as in the reaction of copper(I) with (24), the ligand is reduced to the radical anion (24 ). The dicationic species (25) (only ipso carbon of the phenyl represented) comprises three copper(I) centers and a (24 ) radical anion. The reaction of (18) with [Cr(CO)e] yields the trinuclear star [(18) Cr(CO)4 3] together with dinuclear and mononuclear species. The trinuclear complex with terminal dicyanamide ligands [(18) Co(N(CN)2)2 3] has also been reported and structurally characterized. ... 

A diversity of ID, 2D, or 3D copper assemblies can be obtained, including coordination polymers, as well as multi- or mononuclear species with discrete molecules. Among the latter, the tetranuclear /r-oxo complex derived from triethanolamine [OCu4(tea)4(BOH)4][BF4]2 (Scheme 2.3c) is particularly active (TONs or yields up to 380 or 39%, respectively, for the conversion of cyclohexane to cyclohexanol and cyclohexanone) [33, 34]. It is also active (although less effectively, by one order of magnitude) for the oxidation of methane and ethane to methanol and ethanol, respectively [34]. 

As a part of their ongoing investigations into the reaction of dioxygen with copper(I) complexes to identify copper-superoxo/peroxo intermediate species, Schindler and co-workers51-53 have also provided examples of a number of mononuclear copper(II) complexes (Table 1) (as well as copper(I) Section 6.6.4.2.1). 

From this perspective they reported the structure (complex (791) Cu-Cu 10.061 A) of a m-xylyl-based TACN ligand.583 Structures of four mononuclear copper(I) complexes ((792)-(795)), supported by tridentate macrocycle, were also reported by this group. They investigated their oxygenation behavior and in each case clean formation of side-on peroxo-dicopper(II) species was demonstrated.416... 

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