Copper complexes pyridyl

Copper-complexes prepared with other type of N-chelating ligands have been also prepared and evaluated as catalysts for the Diels-Alder reaction. Eng-berts et al. [103] studied enantioselective Diels-Alder reaction of 3-phenyl-l-(2-pyridyl)-2-propen-l-one with cyclopentadiene in water (Scheme 39). By using coordinating chiral, commercially available a-amino-adds and their derivatives with copper salts as catalysts, they obtained the desired product with yields generally exceeding 90%. With L-abrine (72 in Scheme 39) as chiral moiety, an enantiomeric excess of 74% could be achieved. Moreover, the catalyst solution was reused with no loss of enantioselectivity. 

The complex trans-[Cun(hfac)2(TTF—CH=CH—py)2](BF4)2-2CH2Cl2 was obtained after 1 week of galvanostatic oxidation of Cun(hfac)2(TTF CH=CH py)2 [61]. The molecular structure of the copper complex is identical to its neutral form. There is one TTF CH=CH py molecule per BF4 and one dichloromethane solvent molecule. The copper is located at the center of a centrosymetric-distorted octahedron two TTF CH=CH py ligands in trans- conformation are bonded to Cun by the nitrogen atoms of the pyridyl rings. From the stoichiometry, the charge distribution corresponds to fully oxidized TTF CH=CH—py+" radical units. 

Copper complexes of thioureas and N-substituted thioureas have also been suggested to account for the effectiveness of the parent compounds as antitubercular agents [537]. On the other hand, Ueno [538] suggested that the parent thioureas acted by removing copper from some M. tuberculosis copper-dependent enzyme and that the antitubercular activity was dependent on the relative stabilities of the enzyme complex and thiourea complex. However, the activities of two series of N-substituted (2-pyridyl and 4-pyryl) thioureas [539] could not be correlated with copper complex stability [540]. 

The bipyridyl groups could be used as coordination sites, while pyridyl sites could be protonated to incorporate specific negatively charged chelating ligands. These films were used to analyze for iron and copper complexes in solution. 

Copper complexes of bis(2,2 -dipyridyl)dithiocarbamate have been prepared upon insertion of carbon disulfide into the copper-nitrogen bonds of the corresponding 2,2 -dipyridylamine (dpa) complexes (195, 196). Kumar and Tuck (195) initially noted this behavior for [Cu(dpa)] , [Cu(dpa)2], and [Cu(dpa)(dppe)l [dppe = l,2-bis(diphenylphosphino)ethane], but characterization was made only on the basis of the presence of characteristic v(C—S) and v(C—N) bands in their IR spectra. Later, this was confirmed by the X-ray crystal structure of [Cu(S2Cdpa)2], formed upon slow evaporation of a carbon disulfide solution of [Cu(dpa)2] (Eq. 21) (196). The transformation is actually quite complex as in the dpa complex, metal coordination is through the nitrogen atoms of the pyridyl rings (197), and thus a rearrangement to the amide form must occur prior to carbon disulfide insertion. 

Figure 1 Iron and copper complexes with bis- and tris-pyridyl amino and imino thioether ligands. ...

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Copper(II) complexes of 2,6-lutidylphenylketone thiosemicarbazone, 38, have been prepared from copper(II) chloride and copper(II) bromide [186]. Similar to 2-pyridyl thiosemicarbazones, 38-H coordinates via the ring nitrogen, the azomethine nitrogen and the thiol sulfur based on infrared spectral assignments. Magnetic susceptibilities and electron spin resonance spectra indicate dimeric complexes and both are formulated as [Cu(38-H)A]2 with bridging sulfur atoms. The electronic spectra of both halide complexes show band maxima at 14500-14200 cm with shoulders at 12100 cm S which is consistent with a square pyramidal stereochemistry for a dimeric copper(II) center. 

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