Yea, the distances of coordination bond formed between ligand and metal affect the binding affinity

Rachal Cmp, 

Your question is not very clear. What binding affinity are you referring to? Do you mean link binding affinity of your complex to substrates or for example it's binding affinity to protein etc?

Or are you referring to the binding affinity of the ligand donor atom to the metal ion in the complex?  I ask because depending on which of the possibilities there are other factors that might play a major role rather than the bond length.  

For example,  the bond length in itself might not be a factor but the consequence of some other interactions.  So, that the bond length is long will simply be an indication that the integration between the donor atom and the metal is not strong.  So you can not really say that the long bond length is the reason the affinity of the donor atom is low,  rather you say the long bond length is an indication that the interaction or affinity is low.  And that low affinity might be because of something else.  This later illustration is on the premises that the affinity you are referring to is the ligand binding affinity to the metal center.  

So feel free to clarify which affinity you are talking about and I might give more illustration that might be helpful.  You can also give a typical example of what you are talking about.  

Thanks