Effect of Entering Ligand

There have been extensive studies of the influence of an entering ligand on its rate of entry into a Pt(ll) complex.The rate constants for reaction of a large number and variety of ligands with trans-Pt(py)2C 2 have been measured (Table 4.13). The large range of reactivities is a feature of the associative mechanism and differentiates it from the behavior of octahedral complexes. The rate constants may be used to set up quantitative relationships. For a variety of reactions of Pt complexes in different solvents (Sec. 2.5.4)  

The term s is the nucleophile discrimination factor. The values of pt, the nucleophilic reactivity constant, is useful for correlating kinetic data for other Pt(II) complexes. 

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While the trans effect is the major factor governing square-planar substitution reactions other factors contribute. These factors are the electronic effect of cis ligands (generally relatively unimportant), leaving-group effects, effect of the entering ligand, and solvent effects. 

The ligand field stabilization energy is only one aspect of the formation of a transition state. Because the reactions are carried out in solutions, solvation of the transition state and the entering ligand may have enough effect to assist in the formation of a particular transition state. Also, the fact that some... 

Consider the effect of every impurity or potential impurity in every feedstock, in the solvents in the ligand and in the catalyst. What harm, if any, will befall the product or catalyst if these impurities enter the process, and in particular, if they accumulate Is the product stable in both the reaction and separation system If byproducts form, what affect will they have on the process and catalyst life ... 

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