Coordination compounds factors affecting

Magnetic Studies of Coordination Compounds Factors Affecting the Nature of Bonds Between Nickel and Certain Non-Metallic Atoms. 

The most common reaction exhibited by coordination compounds is ligand substitution. Part of this chapter has been devoted to describing these reactions and the factors that affect their rates. In the solid state, the most common reaction of a coordination compound occurs when the compound is heated and a volatile ligand is driven off. When this occurs, another electron pair donor attaches at the vacant site. The donor may be an anion from outside the coordination sphere or it may be some other ligand that changes bonding mode. When the reaction involves an anion entering the coordination sphere of the metal, the reaction is known as anation. One type of anation reaction that has been extensively studied is illustrated by the equation... 

Other theoretical considerations for synthetic coordination chemistry (isolobal and isoelectronic analogies, chelate, cis and trans effects, factors affecting the acid/ base properties of coordination compounds, bond theories, etc.) are covered in detail in excellent recent monographs [3,34b,104,106] and, for this reason, are not presented in this book. 

The results of chromate reduction by the model compounds listed in Table 2, allow us to predict the environment that the SH groups in a protein will require for them to react readily with chromate. The fastest reductants (Table 2) are either neutral (e.g., cysteine, penicillamine) or have a positive charge (cysteamine). However, charge is not the only factor affecting the kinetics, since the cysteine-chromate reaction is faster than the cys-teamine-chromate reaction and the unithiol-chromate reaction is faster than the DTT-chromate reaction. The obvious advantage that cysteine has over cysteamine is its ability to chelate intermediate Gr species after the disulfide bond has been formed, as illustrated in Fig. 3. Such chelation would facilitate the change in coordination number required in going from Cr(VI) to Cr(IV) or Cr(III) (see Sect. 2). 

An important factor affecting redox potentials is also ion pairing, which is conventionally taken into account in terms of activity coefficients. For redox potentials of coordination compounds, the following equation is known [70] ... 

Phosphorus-substituted carborane ligands can be mono-, bi-, or multidentate when they react with a metal center. Factors affecting this behavior include the structural features of the carborane cage (i.e., whether it is the ortho, meta, or para isomer, or has the closo or nido structure), the substitution pattern of the carborane cluster, the number and kind of donor atoms, and the electronic and steric properties of the ligand. All these factors have an influence on the catalytic activity of the metal complex. For example, the carborane cluster can act as an electron acceptor or electron donor at the phosphorus atom [22,29]. The donor atoms adjacent to phosphorus can act as labile ligands that block the coordination site at the metal until a substrate approaches. In nido cluster compounds, the metal ion can bind in two ways through the phosphorus substituent or by the decapped face of the cluster, whereby the former option is the most stable. In nido-carborme chemistry, B-H-Rh and... 

Factors affecting the acid/base properties of coordination compounds... 

If the identity of the backscatterer is known, then the interest is in determining the number of near neighbors. In this case, one needs to compare the amplitude of the EXAFS of the material of interest (unknown) to that for a compound of known coordination number and structure. However, unlike transferability of phase, which is generally regarded as an excellent approximation, the transferability of amplitude is not. This is because there are many factors that affect the amplitude and, except for the case of model compounds of very similar structures, these will not necessarily (and often will not) be the same. As a result, determination of coordination numbers (near neighbors) is usually no better than 20%. 

Pcs are one class of such compounds with their delocalized two-dimensional 18 7t-electron systems and exceptional stabilities, which make them suitable candidates for NLO applications. From this point of view, Pcs, subphthalocyanines, and related compounds have been investigated extensively in recent years [14]. Besides the excellent 18 Tt-electron systems, the substituents at the benzene rings, coordinative metal, and axial coordination ligands of the Pcs affect the degree of the NLO properties significantly. However, correlation between these factors has not been fully established yet. 

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