The effect of changing the incoming ligand on the rate of ligand substitution in a coordination complex can be significant. The rate of ligand substitution depends on several factors, including the nature of the incoming ligand, the nature of the leaving ligand, and the metal center involved in the complex. The incoming ligand can affect the rate of substitution by altering the stability of the transition state and the overall reaction rate.Experimental evidence supporting the effect of the incoming ligand on the rate of ligand substitution can be found in the study of the "trans-effect" and "labile" and "inert" complexes.1. Trans-effect: The trans-effect is an experimental observation in which certain ligands, when bound to a metal center, can increase the rate of substitution of the ligand trans to them. For example, in a square planar complex, if the incoming ligand has a strong trans-effect, it can significantly increase the rate of substitution of the ligand opposite to it. This effect is attributed to the ability of the incoming ligand to stabilize the transition state of the reaction, making it easier for the leaving ligand to be replaced.2. Labile and Inert Complexes: Coordination complexes can be classified as labile or inert based on their rates of ligand substitution. Labile complexes undergo rapid ligand substitution, while inert complexes exhibit slow substitution rates. The nature of the incoming ligand plays a crucial role in determining the lability or inertness of a complex. For example, complexes with weak-field ligands such as halides are generally more labile, while those with strong-field ligands such as ammonia or carbon monoxide are more inert.Experimental evidence can be obtained by comparing the rates of ligand substitution for different incoming ligands in a series of complexes. For example, one could measure the rate of substitution for a series of octahedral complexes with varying incoming ligands and observe how the rate changes with the nature of the incoming ligand. This can be done using techniques such as UV-Vis spectroscopy or NMR spectroscopy to monitor the progress of the reaction and determine the rate constants.In conclusion, the effect of changing the incoming ligand on the rate of ligand substitution in a coordination complex can be significant, as it can alter the stability of the transition state and the overall reaction rate. Experimental evidence supporting this effect can be found in the study of the trans-effect and the classification of complexes as labile or inert based on their rates of ligand substitution.