Tetranuclear copper complexes

The suggested mechanisms of the various catalytic Click reactions involve the formation of dinuclear or tetranuclear copper complexes (162,163) as the catalyst (Fig. 11) and the creation of a Cu—C bond or a Cu=C bond in the intermediate species (49,121,122,162-166). DFT calculations were used to ascertain the relative stabilities of such complexes (163), showing that the mononuclear complex was more stable than the polynuclear complex. 

Tetranuclear copper complexes have tetrahedral, square-planar, or butterfly structures. The compound Cu4 (Pr 0)2PS2 4 has a distorted tetrahedral skeleton of the metal atoms with one sulfur atom symmetrically bonded to two copper atoms, while the other sulfur atom forms a bond with the third copper atom. Copper and silver form many clusters containing alkyl and aryl ligands (See Chapter 4). The complex Cu4(CH2SiMe3)4, like Cu4 N(SiMe3)2 4, has a square-planar structure with bridging alkyl ligands. In the alkyl compound, in contrast to the amide one, there are Cu —Cu bonds. 

Scheme 4 Formation of mono-, di-, tri-, and tetranuclear olefin-copper complexes.

Ziessel, R., Charbonniere, L., Cesario, M., Prange, T. and Nierengarten, H. (2002) Assembly of a face-to-face tetranuclear copper(I) complex as a host for an anthracene guest. Angew. Chem., Int. Ed., 41, 975. 

Di- and tetranuclear Cu(II) complexes were obtained on reaction of 3 with two and four equivalents of Cu(II), respectively. The former complex has a similar structure to the dinuclear nickel complex mentioned above, although the presence of Jahn-Teller distortion is also evident in the copper complex. 

Synthesis of Dinuclear and Tetranuclear Copper(ll) Complexes of 2,6-Diformyl-4-methylphenol-di(benzoylhydrazone) [256b]... 

Multimetallic complexes (tetranuclear and pentanuclear with complicated structures) of these ligands which could have unique magnetic properties were prepared and studied. It is noted [125a] that, in the copper complex with H2L, Cu5(0H)2(L)2(N03)4, all magnetic interactions within the complex unit H2L appear to be antiferromagnetic, as well as in copper complexes with two other ligands, [Cu(HL1)(N03)]4 and [Cu2(L2)(OAc)2]2 [187,188],... 

The molecular structure of the dark blue derivative [(thd)Cu(OC2H4OMe)]4 formed by the reaction of [(thd)Cu(0-/-Pr)]2 with 2-methoxyethanol is shown in Fig. 59. This structure represents an example of a less common double-chain ladder, such as the centrosymmetrical tetranuclear copper(II) complex (379) with a complete sixfold coordination of the inner copper(l) and copper(la) atoms. 

Carboxamides containing alkylamine arms like (34), synthesized from dialkylmalonate and ethylene-diamine, act as chelating dianionic N4-donors,44,45 whereas the geometric isomer (35) was prepared from 1,3-diaminopropane and chloroacetyl chloride.46 The hexadentate bis(pyrazine)-carboxamides (36) and (37) can be obtained by the addition of 1,3-propanediamine to the appropriate carboxylic acid.47 Compound (36), in the dianionic form, can be used to obtain homo- and hetero-metal bridged complexes, whereas (37) has been shown to yield tetranuclear copper(II) complexes involving opened-up dianionic ligand molecules.47... 

The tetranuclear copper(Il) complex 8 [38,40], prepared with /1-alanine-hydroxamic acid, displays an almost planar conformation of the macrocycle. Schematic diagrams of [9]crown-3 (9-C-3) 9 and [12]crown-4 (12-C-4) 10 are compared with the analogous cores of the metallacrovms [9]metallacrown-3 (9-MC-3) 7 and [12]metallacrown-4 (12-MC-4) 8. 

A possible explanation for such an unusual kinetic behavior is the following. Disproportionation of two molecules of the bis(//-oxo)dicopper(III) complexes may afford one molecule of (/i-oxo)(/i-oxyl radical)dicopper(III) (A in Scheme 9) and one molecule of bis(/u-oxo)Cu(II)Cu(III) (B in Scheme 9), the former of which may be the real active species for the C—H bond activation (hydrogen atom abstraction) of the substrates (Scheme 9). " Alternatively, two molecules of the bis(/i-oxo)dicopper(III) intermediate may function in unison (e.g., via a tetranuclear copper-oxo complex) to oxidize the substrate. " ... 

The synthesis of the tetranuclear copper(I) complex, [Cu(dppz)]4, (Hdppz = 3,5-diphenylpyrazole), its crystal structure and catalytic properties in the oxidation of settled organic molecules will be presented and discussed. 

E. Colacio, M. Ghazi, R. Kivekas, and J. M. Moreno, Helical-chain copper(II) complexes and a cyclic tetranuclear copper(II) complex with single syn-anti car-boxylate bridges and ferromagnetic exchange interactions, Inorganic Chemistry, vol. 39, no. 13, pp. 2882-2890, 2000. 

Hermann A, Silva LS, Peixoto CRM, Oliveira ABD, Bordinhao J, Homer M (2008) Electrochemical properties of Cu4[PhN3C6H4N3(H)Ph]4(p-0)2, a tetranuclear Copper(II) complex with l-phenyltriazenido-2-phenyltriazene-benzene as ligand. Eclet Quim 33(3) 43 6... 

On the other hand, the first luminescent tetranuclear copper(I) sulhdo complex [Cu4(p-dppm)4( i4-S)] (12a) was reported by us in 1993 [65]. The X-ray crystal structure of the complex reveals a p4-bridging mode of the sulfido ligand. This complex, as well as die structural analogs [Cu4(p-dppm)4(H4-Se)] + (12b) [66] and [Cu4( A-dtpm)4( i4-S)] (12c) [67], displays intense and long-lived orange luminescence in the solid state and in fluid solutions upon photoexcitation. The photophysical data are summarized in Table 4. 

Besides, a tetranuclear copper(I) cluster [Cu4 S2P(0 Pr)2 4] (15) with dialky Idithiophosphate as ligands has also been reported to be luminescent [88]. The solid-state emission of the complex occurs at 547 nm at 298 K. At 77 K, dual luminescence at 573 and 647 nm has been observed. 

---