Synthesis An Interplay Between Thermodynamics and Kinetics

Just like any other chemical reactions, synthetic reactions adhere to the principles of thermodynamics the study of energy and its interconversions. Is your desired product thermodynamically stable (can it be made and will it exist at room temperature and atmosphere) Will it be stable under your given synthetic conditions, including during and after isolation Gibb s free energy, AG, is our measure of the driving force for reactions, equation (1.10). 

When the reactants and products are at unit activity, equation (1.10) is expressed with standard state functions, equation (1.11)  

A general expression for metal complex formation is given in equation (1.12). The formation constant, Kt, reflects the thermodynamic feasibility of complex formation. 

For example, the reaction of aqueous iron(III) with the hexadentate ligand, EDTA4-, equation (1.13), has a log Kt = 25.0 (25 °C, 0.1 M ionic strength). The large equilibrium constant tells us that the reaction as written is expected to favor the FeEDTA- product (i.e., the product should be very stable under these conditions in solution)—and it does  

Formation constants for many metal complexes have been compiled by Ramunas Motekaitis and Art Martell, and these as well as techniques for measuring them in the laboratory will be covered in Chapters 3 and 8. One can, however, predict the relative stability of a desired complex based on simple bonding theories. Crystal field theory, as well as the Irving-Williams series and Pearson s hard-soft-acid-base theory (see the next section) enable us to predict what might happen in solution. 

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