Copper complexes pseudotetrahedral

The orange complex 83 (57) exhibits a pseudotetrahedral geometry in the solid state, with the chlorine atoms distorted 49° and 63° away from the bipyridyl-Cu plane (Fig. 8). The d-d transition occurs at 919 nm. It seems likely that the large size of the ligand substituent is responsible for the deviation in the structure of the copper complex. Whether this effect is also responsible for the ease of reduction of the corresponding triflate complex by diazoester is not clear. 

Further interesting redox modified polypyrrole films were prepared e.g. a polymeric copper phenanthroline complex that can be reversibly de- and re-metallated because it retains the pseudotetrahedral environment after decomple-xation, A very diversified electrochemistry is displayed by polypyrrole films containing electron donor as well as electron acceptor redox centers in the same film... 

The copper(I) analogue [Cu(L)][C104] (744) (distorted tetrahedral) of copper(II) complex (201) was also synthesized and its redox property investigated.193 Structuresof complex (745) (distorted tetrahedral)557 and complex (746) (pseudotetrahedral Cu-Cu 4.764 A)558 were also reported. 

The copper-alkoxo unit, which is usually synthesized in situ, plays a significant role in metal-promoted transformations of organic substrates by copper(I). To determine the reaction form of the Cu-OPh unit, Floriani and co-workers structurally characterized four complexes (772) (pseudotetrahedral Cu-Cu 3.223 AT (773) (pseudotetrahedral), (774) ( anion linear coordination) and (775) (planar trigonal).57 Using 3,3,6,6-tetramethyl-l-thia-4-cycloheptyne as terminal ligand the structural characterization of a copper(I)-alkyne complex (776) (Cu-Cu 2.940 A) was reported.573... 

A binuclear complex of 4-methyl-l,8-naphthyridine (150) has been prepared.1 100 Its structure, as determined by X-ray diffraction, shows two nearly equivalent copper atoms in a pseudotetrahedral environment bridged by one chlorine and two 4-methyl-1,8-naphthyridine rings. 

Pseudotetrahedral complexes such as 17 (Scheme 1.17) were observed to possess a particularly rich substitution chemistry [37]. Complex 17 reacted cleanly with o-phenylenediammonium to give the covalent substitution product 18 shown in Scheme 1.17. This imine substitution was driven by the same pk, effect employed in the l-to-2 transformation of Scheme 1.2. In addition, 17 reacted cleanly with copper bis(biquinoline) complex 10 to give the coordinative substitution product 20. This ligand exchange appears to have been sterically driven the substitution of one of the encumbering di(imine) ligands for a less bulky biquinoline provided the driving force for this reaction [45],... 

Pseudotetrahedral complexes of Cu1, [Cu(bpy)2]BF4 and similar derivatives with substituted dipyridyl ligands all gave intact cations in their ES mass spectra [37,38]. In an extension of this chemistry, bipyridyl groups were introduced into amino acid residues and, after reaction with Cu1, the intact cations of the copper(I) complexes of these species were observed [37]. The analogous [Cu(phen)2]+ ion and others derived from substituted phenanthrolines have also been observed [39]. For both the [Cu(bpy)2]+ and [Cu(phen)2] + species, collisional activation led to loss of one ligand. 

The effect of metal ion stereochemical preference in mediating the final structure of a self-assembling helix was examined by Williams and coworkers using the ligand (20) [26]. The formation of a double-hehcal structure is seen from the reaction of two equivalents of copper(I) and two equivalents of (20) (Figure 8). This structure, with pseudotetrahedral geometry around the metal centers, was found to exist in solution by UV-visible spectroscopy, H NMR and cyclic voltammetry. The double helix does not appear to be the only species existing in solution mononuclear [Cu(20)J+ was observed by H NMR spectroscopy. The H NMR spectrum of the complex between copper(I) and... 

The ability of copper(I) to form pseudotetrahedral coordination complexes with bipyridine units has recently been used to design several unusual complexes. When [Cu(OTF)2 CgH6] is allowed to complex with the ligand... 

Finally, a pseudotetrahedral complex more closely resembling the copper site in blue copper proteins, including the presence of two cysteine groups, can be achieved by using a cysteine derivative of ethylenediamine, [HSCHjCHfCOjCHjJNHCHjlj. It is a softer, polydentate (though not macrocydic) ligand and will displace N4 ... 

Many (although not all) spectroscopic data on metal-substituted derivatives and their binary and ternary complexes have also been interpreted as indicative of a four-coordinate metal.Even nickel(II) and copper(II), which have little tendency to adapt to a pseudotetrahedral ligand environment, do so in LADH, the electronic structure of the latter resembling that of blue proteins (Figure 2.36). ... 

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