Copper chain structures

In connection to the data described earlier, one reasonable question arises Why does the stabilizing role of a nonaqueous solvent become significant for Cu salts and remain insignificant for Cu salts It was shown (Myagchenko et al. 1989) that Cu salts (and salts of Hg and Pd as well) exist in nonaqueous solutions as polynuclear compounds. Thus, CUCI2 forms lamellar lattices with chlorine chains as bridges between copper atoms. In contrast, CuCl does not form such chain structures. 

Bonding Agents. These materials are generally only used in wire cable coat compounds. They are basically organic complexes of cobalt and cobalt—boron. In wire coat compounds they are used at very low levels of active cobalt to aid in the copper sulfide complex formation that is the primary adherance structure. The copper sulfide structure builds up at the brass rubber interface through copper in the brass and sulfur from the compound. The dendrites of copper sulfide formed entrap the polymer chains before the compound is vulcanized thus holding the rubber firmly to the wire. 

While the structures so far described in Figure 4.1-4.7 involve distinct molecular and polynuclear copper(I) species, they are characterized by the relatively low coordination numbers of two, three and four. Such low coordination numbers are conducive10 to bridging ligand functions and hence to infinite lattices involving chains (or ribbons), sheets and three-dimensional lattices.199 Figure 4.8 summarizes the types of chain structures characteristic of copper(I). 

Metal ions having coordination number two occur in Hg(CN)2, [Ag(CN)2]- and [Au(CN)2]-, all derivatives of d ° species in each case the structure is linear. In K[Cu(CN)2] the copper atom is actually three-coordinated, the anion being an infinite chain each copper has a carbon atom of an unshared cyanide, and a carbon atom and a nitrogen atom of shared cyanides, as nearest neighbours in approximately planar coordination. Three-coordination also occurs in the [Hg(CN)3]- ion, but there are weak interactions between two of the nitrogen atoms and mercury atoms of other anions, giving rise to a loosely bonded chain structure. 

Leznoff and co-workers reported the structural characterization and the polymorphic nature of a gold(I)-copper(II) coordination polymer, [Cu Au(CN)2 2(dmso)2] 00 [125]. In a green polymorphic form it possessed a 1-D chain structure with five-coordinate copper(II) centers, while a 2-D corrugated sheet structure with six-coordinate copper(II) centers was characterized in the blue polymorph, both of which are linked together to form a 3-D structure via aurophilic interactions. These two polymorphs exhibited virtually identical vapochromic behavior towards water, MeCN, dioxane, dmf, pyridine and ammonia, with the formation of [Cu Au(CN)2 2(solvent)x]oc,. 

Copper(I) Carboxylates, Triflate, Alkoxides, and Dialky lamides. Thecarbox-ylates have varied structures. The acetate that is obtained as white air-sensitive crystals by reduction of Cu11 acetate by Cu in pyridine or MeCN has a planar chain structure (17-H-I). By contrast the trifluoroacetate [Cu02CCF3]4-2C,H6, and benzoate [Cu02CPh]4 complexes are tetramers with bridging carboxylates as in (17-H-II). This is only one type of Cut polynuclear structure (see later). There are also bridged pyrazole and pyrazolylborate compounds. 

Compounds 1 and 2 are closely related to each other. Both exhibit linear chain structures in which the Cu2(hedp)2 dimers are connected by edge-shared CuOs square pyramids (Fig. la). Each hedp in the chains behaves as a bis(chelating) bridging ligand and links two copper ions in a c/s-bridging mode. This is different from the traw-bridging mode... 

Temperature dependent conductivity studies reveal a metallic character of the salt and the remarkably high conductivity of 500000 S/cm at 3.5 K. It should be noted that the TCNQ copper salt is a semiconductor with a room-temperature conductivity of 2x 10 S/cm. The crystal structure of the salt TCNQI 2Cu reveals segregated columns formed from the quinone and the copper ion whereby the copper chains are surrounded by 4 quinone stacks [344]. 

Black copper(II) thiocyanate turns red-brown on heating, and it is postulated that the product is derived from copper(I) thiocyanate distorted by the inclusion of thiocyanogen in the lattice (395). A zigzag chain structure analogous to AgSCN (492) has been suggested for CuNCS on the basis of their similar infrared spectra (502). 

Figure 3.21 The chain structure of [PrCu2(pic)4(H20)6] "+ [Pr, black (large ball) Cu, black (medium balls) O, grey N, black (small balls) C, white H, omitted)]. (Redrawn from the CIF file of A.Q. Wu et al., Extended structures and magnetic properties of lanthanide-copper complexes with picoUnic acids as bridging ligands, European Journal of Inorganic Chemistry, 2005 (10), 1947-1954, 2005 [81].)...

The low stability of two-coordinate complexes with respect to other possible structures is well illustrated by the cyano complexes. Although silver(I) and gold(I) form discrete bis(cyano) complexes, solid KCu(CN), possesses a chain structure in which the coordination number of the copper(l) is 3. 

Heating [Zn(dmpz)2(Hdmpz)]2, 31, at 240°C (see Fig. 5) caused the loss of Hdmpz and the formation of the species [Zn(dmpz)2] , 25 (42). Complex 25 is assumed to be polymeric, with an infinite chain structure, by analogy with the known structure of other binary copper(II) pyrazolates (35). 

Fig. 15a and b. EXAFS determined copper oxalate structure a) ribbon structure of the chains b) 3D packing of the ribbons... 

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