Dimeric structures copper complexes

In the reactions of 10.13a with alkali metal terr-butoxides cage expansion occurs to give the sixteen-atom cluster 10.15, in which two molecules of MO Bu (M = Na, K) are inserted into the dimeric structure. The cluster 10.13a also undergoes transmetallation reactions with coinage metals. For example, the reactions with silver(I) or copper(I) halides produces complexes in which three of the ions are replaced by Ag" or Cu" ions and a molecule of lithium halide is incorporated in the cluster. ... 

Encapsulated Cu—chlorophthalocyanines oxidize hexane at C-l using 02 and at C-2 using H202 as oxidants. The dimeric structure of copper acetate is intact when it is incorporated into the zeolite. This is a regioselective aromatic hydroxylation catalyst, which mimics the specificity of the monooxygenase enzyme tyrosinase.82,89 Zeolite NaY catalysts made with a tetranuclear Cu(II) complex were synthesized and characterized.90... 

The X-ray crystallographic analysis of 2 -Cu reveals a dimeric structure, where two copper ions are coordinated to two ligand molecules (Fig. 8). Each copper ion is situated in a trigonal planar carbene/alkenyl carbon ligand environment, coordinated to two carbene arms from one chelator and a third carbon from the pendant arm of a second chelator. The average Cu—C bond distance is 1.996 (1)A, consistent with that of other reported Cu(I) carbene complexes (29). 

While there are no crystal structures of mononuclear Schiff base complexes of copper(I) (N—O ligands) available, these do occur as in the dimeric structure of... 

In the past ten years it is probably (ii) and (iii) above that have provided the major incentive in the synthesis of novel dimeric structures in copper(II) systems.30 Reference 10 includes a review of polynuclear copper(II) complexes in general and ref. 30 includes reference to a large range of biologically relevant dinuclear copper(II) complexes. The structural chemistry of binuclear copper(II) complexes was reviewed in 1977.586 In order to systematize the description of copper(II) polynuclear structures the following notation is introduced. 

The high affinity shown by carboxylic acids for copper (II) compared with the remaining divalent metals of the first transition series appears to be due in part to the stabilization of the extracted complexes by the formation of the well-known dimeric structure (1) in which copper(II) carbox-ylates exist in the solid state and in non-donor solvents.54 The axial ligands, L, consist of undissociated carboxylic acid molecules55 or, in the absence of an excess amount of extractant, they may consist of water or other solvent molecules.56 Copper was successfully removed from nickel sulfate solutions on the base-metal plant at Matthey Rustenburg Refiners in South Africa by being extracted into Versatic 10 acid at a controlled pH value. The process is believed to have been discontinued only because improvements in the selective leaching of copper and nickel rendered it unnecessary. 

The structure of 73 was substantiated spectroscopically (5 nB = 82.5 ppm) and confirmed crystallographically. A centrosymmetric chloro-bridged dimeric structure with tricoordinate copper centers was observed. The pendant character of the borane is apparent from the rather long the B- Cu (3.05 A) and B- Cl (4.06 A) distances associated with a trigonal planar geometry around boron. Compared to related mononuclear palladium and rhodium complexes (see Section IV.B), the presence of the chloro-bridge disfavors the formation of Cl-B interactions (coordination mode F) in 73. 

A combination of the two techniques was shown to be a useful method for the determination of solution structures of weakly coupled dicopper(II) complexes (Fig. 9.4)[119]. The MM-EPR approach involves a conformational analysis of the dimeric structure, the simulation of the EPR spectrum with the geometric parameters resulting from the calculated structures and spin hamiltonian parameters derived from similar complexes, and the refinement of the structure by successive molecular mechanics calculation and EPR simulation cycles. This method was successfully tested with two dinuclear complexes with known X-ray structures and applied to the determination of a copper(II) dimer with unknown structure (Fig. 9.5 and Table 9.9)[119]. 

In contrast to the lithium acetylide reaction, addition of copper(I) phenylacetylide to (i75-C5H5)(PPh3)2RuCl (1) affords the monomeric ruthenium acetylide-copper chloride adduct (62) as the major product. An X-ray crystal structure of this complex reveals an tj1, -bridging acetylide between the ruthenium and copper centers, respectively (62). A small amount of the dimeric chloride bridged complex 61 was also isolated. The copper chloride can be removed from the monomeric complex by the... 

EPR spectra recorded for solutions of different pH were simulated on the basis of the assumption of coordination spheres with different compositions and structures. These measurements indicated the coordination of one N donor atom to copper(II) at pH > 6 in MLH.2, and dimerization of the complex between pH 6 and 10 (M2L2H 4, M2L2H.3). The EPR spectra also reflected the decomposition of the dimeric species at pH > 10, i.e. the formation of MLH.3. 

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