Cu2 coordination

The tetrahedral Cu04 group is rarely observed and no strong evidence has ever been presented for this highly symmetrical environment about the divalent copper ion. Coordinations higher than VI (or IV + II) are also very rare. Statistical data for Cu2+ coordination environments in 234 oxysalts and 75 minerals will be summarized. 

Jones CE, Abdelraheim SR, Brown DR et al (2004) Preferential Cu2+ coordination by His96 and Hislll induces beta-sheet formation in the unstructured amyloidogenic region of the prion protein. J Biol Chem 279 32018-32027... 

Cu2+ coordination cluster model with constraint positions of terminal OH groups... 

Cu2+ coordination hybrid QM-pot model employing 6-T cluster model... 

Drew SC, Masters CL, Barnham KJ (2009) Alanine-2 carbonyl is an oxygen ligand in Cu2+ coordination of Alzheimer s disease amyloid-beta peptide—relevance to N-terminaUy truncated forms. J Am Chem Soc 131 8760-8761... 

The nitrogen atom of each NH3 molecule contributes a pair of unshared electrons to form a covalent bond with the Cu2+ ion. This bond and others like it, where both electrons are contributed by the same atom, are referred to as coordinate covalent bonds. 

The behaviour of polydentate ligands containing sulphinyl groups has received much less attention. Giesbrecht and Osorio203 have reported the coordination compounds of bivalent transition metal (Mn2+, Co2+, Ni2+, Cu2 +, Cu2+, Zn2+) perchlorates with 2,2 -sulphinyldiethanol (SDE). 

Bidentate sulphoxides, such as 1,3-bis(methylsulphinyl)propane, 1,4-bis(methyl-sulphinyl)butane and 1,2-bis(ethylsulphinyl)ethane, have been synthesized and employed as ligands toward Mn2 +, Co2 +, Ni2 +, Cu2 + and Zn2 + 204. All metal ions are bound to the ligands via the oxygen of the sulphoxide groups and are six-coordinate, as shown in Scheme 20, with the exception of Cu2+, which is four-coordinate. 

The enantioselectivity of this catalyst, which is prepared as the iodide salt, is somewhat dependent on the anion that is present. If AgSbF6 is used as a cocatalyst, the iodide is removed by precipitation and the e.e. increases from 81 to 91%. These results indicate that the absence of a coordinating anion improved enantioselectivity. Entry 2 shows the extensively investigated f-BuBOX ligand with an A-acryloylthiazolidinone dienophile. With Cu2+ as the metal, the coordination geometry is square planar. The complex exposes the re face of the dienophile. 

Cu2+(aq) to 0.9 in [Cu(tetb)]2+. There is also a modest increase in softness due to changes in EA and CA parameters, which can be interpreted in terms of the symbiosis proposed by Jorgensen (33). The low Da parameter for [Cu(tetb)]2+ suggests that the main effect in transforming Cu(II) to a soft Lewis acid in [Cu(tetb)]2+ is the altered steric situation in coordination of bulky donor atoms to the metal ion. 

In Fig. 9.4 the additional stabilization by the Jahn-Teller effect has not been taken into account. Its inclusion brings the point for the (distorted) octahedral coordination for Cu2+ further down, thus rendering this arrangement more favorable. 

Taking into account the electron density relocation (Table 2.4) two routes of NO adsorption can be distinguished. Thus, the nitric oxide coordinates to the monovalent Cr, Ni, and Cu ions in an oxidative way (A<2M > 0), whereas for the rest of the TMIs in a reductive way (AgM < 0). Although this classification is based on the rather simplified criteria, it is well substantiated by experimental observations. Examples of reductive adsorption are provided by interaction of NO with NinSi02 and NinZSM-5, leading at T > 200 K to a Ni -NOs+ adduct identified by the characteristic EPR signal [71]. At elevated temperatures, similar reduction takes place for ConZSM-5 [63], whereas in the case of Cu ZSM-5 part of the monovalent copper is oxidized by NO to Cu2+, as it can readily be inferred from IR and EPR spectra [72,73], This point is discussed in more detail elsewhere [4,57],... 

Wen XG, Zhang WX, Yang SH (2002) Solution phase synthesis of Cu(OH)2 nanoribbons by coordination self-assembly using Cu2S nanowires as precursors. Nano Lett 2(12) 1397—1401... 

Mapsi et al. [16] reported the use of a potentiometric method for the determination of the stability constants of miconazole complexes with iron(II), iron(III), cobalt(II), nickel(II), copper(II), and zinc(II) ions. The interaction of miconazole with the ions was determined potentiometrically in methanol-water (90 10) at an ionic force of 0.16 and at 20 °C. The coordination number of iron, cobalt, and nickel was 6 copper and zinc show a coordination number of 4. The values of the respected log jSn of these complexes were calculated by an improved Scatchard (1949) method and they are in agreement with the Irving-Williams (1953) series of Fe2+ < Co2+ < Ni2 < Cu2+ < Zn2+. 

Chemical bonds can have covalent character, and EPR spectroscopy is an excellent tool to study covalency An unpaired electron can be delocalized over several atoms of a molecular structure, and so its spin S can interact with the nuclear spins /, of all these atoms. These interactions are independent and thus afford additive hyperfine patterns. An unpaired electron on a Cu2+ ion (S = 1/2) experiences an / = 3/2 from the copper nucleus resulting in a fourfold split of the EPR resonance. If the Cu is coordinated by a... 

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