Complex ions coordinate bonding

Polymer-metal complexes often exhibit high efficiency in the catalytic decomposition of hydrogen peroxide. The following reasons for this activity have been advanced, (i) Some polymer-metal complexes contain incomplete complexes due to steric hindrance, and this contributes to their catalytic activity121, 122. (ii) In other polymer complexes, the coordinate bond between polymer ligand and metal ion is relatively weak and the substrate coordinates with high frequency124. ... 

In the polymer complex, the coordinate bonds between the Cu(II) ion and the polymer ligand are probably weakened by the strain produced in the polymer-ligand chain by electrostatic repulsion between the cations on the polymer chain or by the steric bulkiness of the polymer ligand. Thus, less energy is required to stretch the coordinate bonds and electron transfer occurs more easily than in the monomeric analogue. 

The Cu(NH3)42+ ion is commonly referred to as a complex ion, a charged species in which a central metal cation is bonded to molecules and/or anions referred to collectively as ligands. The number of atoms bonded to the central metal cation is referred to as its coordination number. In the Cu(NH3)42+ complex ion—... 

Figure 15.2 (p. 412) shows the structure of the chelates formed by copper(II) with these ligands. Notice that in both of these complex ions, the coordination number of copper(II) is 4. The central cation is bonded to four atoms, two from each ligand. 

Coordination number The number of bonds from the central metal to the ligands in a complex ion, 409,412t four-coordinate metal complex, 413 six-coordinate metal complex, 413-414 Copper, 412 blister, 539... 

The formulated principals correlating crystal structure features with the X Nb(Ta) ratio do not take into account the impact of the second cation. Nevertheless, substitution of a second cation in compounds of similar types can change the character of the bonds within complex ions. Specifically, the decrease in the ionic radius of the second (outer-sphere) cation leads not only to a decrease in its coordination number but also to a decrease in the ionic bond component of the complex [277]. 

Molten salts are characterized by the formation of discrete complex ions that are subjected to coordination phenomenon. Such complex ions have specific compositions that are related to the rearrangement of their electronic configuration and to the formation of partially covalent bonds. The life time of the coordinated ions is longer than the contact period of the individual ions [293]. 

When, however, the ligand molecule or ion has two atoms, each of which has a lone pair of electrons, then the molecule has two donor atoms and it may be possible to form two coordinate bonds with the same metal ion such a ligand is said to be bidentate and may be exemplified by consideration of the tris(ethylenediamine)cobalt(III) complex, [Co(en)3]3+. In this six-coordinate octahedral complex of cobalt(III), each of the bidentate ethylenediamine molecules is bound to the metal ion through the lone pair electrons of the two nitrogen atoms. This results in the formation of three five-membered rings, each including the metal ion the process of ring formation is called chelation. 

Chelants have the ability to take waterborne metal ions such as Ca and Mg (but also Fe and Cu) and produce soluble coordinate bond complexes. Therefore, they can be employed for the control of FW hardness salts and other related problems. 

Organic compound (such as ethylenediamine-tetraacetic acid (EDTA) or nitrilo-triacetic acid (NTA) having the ability to take metal ions in water and produce soluble, coordinate-bond complexes. Chelants are commonly used in BW deposit control treatments and various cleaning formulations. 

Linkage isomerism This is a special type of structural isomerism in which the differences arise from a particular ligand which may coordinate to a metal ion in more than one way. In Table 1-3 we indicated that a ligand such as thiocyanate could bond to a metal through either the nitrogen or the sulfur atom, and the complex ions [Co(NH3)5(ACS)]2+ and [Co(NH3)5(5CN)]2+ are related as linkage isomers. 

The given structure shows two molecules of TTA to have reacted with a cobalt ion to form the cobalt-TTA complex, in which the cobalt atom forms a valence bond solid lines) with one, and a coordinate bond (broken lines) with the other, oxygen atom of each TTA molecule. Thus, in the cobalt-TTA complex there is a six-membered ring formed by each TTA molecule with the cobalt atom. Metal chelate complexes of this type have good stability, they are nonpolar and soluble in the organic phase. The usefulness of the chelating extractants in solvent extraction is therefore obvious. 

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