Thermodynamics metal-ligand bonding

Under these conditions, the formation rate constant, k, can be estimated from the product of the outer sphere stability constant, Kos, and the water loss rate constant, h2o, (equation (28) Table 2). The outer sphere stability constant can be estimated from the free energy of electrostatic interaction between M(H20)q+ and L and the ionic strength of the medium [5,164,172,173]. Consequently, Kos does not depend on the chemical nature of the ligand. A similar mechanism will also apply to a coordination complex with polydentate ligands, if the rate-limiting step is the formation of the first metal-ligand bond [5]. Values for the dissociation rate constants, k, are usually estimated from the thermodynamic equilibrium constant, using calculated values of kf ... 

The determination of the heat capacity of a substance as a function of the temperature is by itself a very important application of DSC, because it may lead to values of the thermodynamic functions S%, //-" — //q, and Gy, mentioned in chapter 2. An example is the study of C6o carried out by Wunderlich and co-workers [271], The application of DSC in the area of molecular thermochemistry has been particularly important to investigate trends in transition metal-ligand bond dissociation enthalpies. The typical approach used in these studies, and its limitations, can be illustrated through the analysis of the reaction 12.27, carried out by Mortimer and co-workers [272] ... 

Poe and co-workers have extensively studied the thermodynamics, kinetics and the trans effect in the reactivity of such complexes.623-634 635 638,64Cl-650-653 The thermodynamics of the successive anations of [Rh(en)2X(H20)]"+ by halogens suggests that the Rh center is a marginally soft acid, and that its softness is increased by the coordination of a soft base (such as I- ) in a position trans to the reaction site a halide ligand weakens the metal-ligand bond trans to itself, and an I- causes a more dramatic weakening than a Br-, which has more effect than a coordinated q-.634,638-640 The spectrophotometrically obtained thermodynamic parameters are summarized in Table 38. 

While metallocenes are often thought to be entirely in the domain of transition metal chemistry, we have shown that main group chemists have a legitimate claim as well. The lack of d orbital participation in the metal-ligand bonding may result in less thermodynamic stability but does not preclude the possibility of novel structural motifs or future real-world applications. Computational... 

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