Metal-ligand complexation reactions

The most important types of reactions are precipitation reactions, acid-base reactions, metal-ligand complexation reactions, and redox reactions. In a precipitation reaction two or more soluble species combine to produce an insoluble product called a precipitate. The equilibrium properties of a precipitation reaction are described by a solubility product. 

Mole-ratio plots used to determine the stoichiometry of a metal-ligand complexation reaction. 

B.l.a. Water eocchange rates. Water-exchange rates are key guides of chemical reactivity in aqueous coordination compounds. Aqueous metal-ligand complexation reactions take place through the diffusion-limited formation of an electrostatic ion pair,... 

Metal-ligand complexation reactions are usually investigated at constant pH and ionic strength using experimental techniques that are able to distinguish the metal-ligand complex from the uncomplexed metal (i.e., from all forms of the ligand tliat are not bound to the metal ion. Thus, a conditional stability constant, or more precisely, a conditional concentration quotient, K, can be written (MacCarthy and Perdue, 1991)... 

Another level of cooperativity can be observed for the chelate effect in terms of bonding of additional chelating ligands, as seen in the examples below. In coordination chemistry, a simple form of cooperativity can be observed in the successive complex formation constants (ATml,) for certain metal-ligand complexation reactions (9 and 10). 

The equilibrium constant for a reaction in which a metal and a ligand bind to form a metal—ligand complex K ). 

The product of this reaction is called a metal-ligand complex. In writing the equation for this reaction, we have shown ammonia as NH3 to emphasize the pair of electrons it donates to Cd +. In subsequent reactions we will omit this notation. 

The formation of a metal-ligand complex is described by a formation constant, K. The complexation reaction between Cd + and NH3, for example, has the following equilibrium constant... 

The concentration of aluminum in serum can be determined by adding 2-hydroxy-1-naphthaldehyde p-methoxybenzoyl-hydrazone and measuring the initial rate of the resulting complexation reaction under pseudo-first-order conditions.The rate of reaction is monitored by the fluorescence of the metal-ligand complex. Initial rates, with units of emission intensity per second, were measured for a set of standard solutions, yielding the following results... 

From a historical perspective it is interesting to note that the Nozaki experiment was, in fact, a mechanistic probe to establish the intermediacy of a copper carbe-noid complex rather than an attempt to make enantiopure compounds for synthetic purposes. To achieve synthetically useful selectivities would require an extensive exploration of metals, ligands and reaction conditions along with a deeper understanding of the reaction mechanism. Modern methods for asymmetric cyclopropanation now encompass the use of countless metal complexes [2], but for the most part, the importance of diazoacetates as the carbenoid precursors still dominates the design of new catalytic systems. Highly effective catalysts developed in... 

Complexation, or chelation, is the process by which metal ions and organic or other non-metallic molecules (called ligands) can combine to form stable metal-ligand complexes. The complex that is found will generally prevent the metal from undergoing other reactions or interactions that the free metal cation would. Complexation may be important in some situations however, the current level of understanding of the process is not very advanced, and the available information has not been shown to be particularly useful to quantitative modeling (5). 

Molecular simulation methods can be a complement to surface complexation modeling on metal-bacteria adsorption reactions, which provides a more detailed and atomistic information of how metal cations interact with specific functional groups within bacterial cell wall. Johnson et al., (2006) applied molecular dynamics (MD) simulations to analyze equilibrium structures, coordination bond distances of metal-ligand complexes. 

Once the optimal metal/ligand/anion combination has been determined, the choice of the metal complex which is actually put into the reaction solution will become of importance. Active hydrogenation catalysts are metal-ligand complexes which can either be prepared in situ simply by mixing a suitable precur-... 

Another area where titration calorimetry has found intensive application, and where the importance of heat flow versus isoperibol calorimetry has been growing, is the energetics of metal-ligand complexation. Morss, Nash, and Ensor [225], for example, used potenciometric titrations and heat flow isothermal titration calorimetry to study the complexation of UO "1" and trivalent lanthanide cations by tetrahydrofuran-2,3,4,5-tetracarboxylic acid (THFTCA), in aqueous solution. Their general goal was to investigate the potential application of THFTCA for actinide and lanthanide separation, and nuclear fuels processing. The obtained results (table 11.1) indicated that the 1 1 complexes formed in the reaction (M = La, Nd, Eu, Dy, andTm)... 

A kinetic description of rapid metal ion complexation reactions. Desolvation of the primary coordination sphere of the metal ion is treated as the rate-limiting step in forming its inner-sphere coordination complex with a ligand. 

METAL IONS IN NUCLEOTIDE-DEPEN-DENT REACTIONS Metal ligand complexation,... 

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