1. Questions

ligands

Is chloride ion or water a stronger ligand?

Clueless


Is water or ammonia a stronger ligand?

Clueless

Is ammonia or ethylenediamine a stronger ligand?

Clueless

I don't really get the idea of ligands; I definitely won't get strenght of ligands. I know ligands replace other ligands...

P.S I know that it is an ion or molecule that binds to a metal to form a complex. Unfortunately, my lab manual does not explain strenght of ligands.


Look in your text for the chapter on coordination compounds. The freshman text I have by Whitten, Davis, Peck lists this order for strengths of ligands with regard to crystal field theory.
I^- <Br^- <Cl^- <F^- <OH^- <H2O <(COO)2^2- <NH3 <en <NO2^- <CN^- where en is ethylenediamine. I hope this helps.


Thank you Dr.Bob... my problem though is that I do not see why it is stronger. For example my lab manual asks why it would be stronger. I just have no clue why? I wrote for the first question that chloride ion is bigger than water molecule (not sure if correct); for the second question, I wrote that ammonia is the same as water molecule(again, not sure why... just guessing) I have finals today (6pm on the dot), I'm afraid a similar question might be on test in lecture. Here is the list of the questions... (I'll look at text again to see where I misread)thx


As far as I know there is no "theory" that goes along with which is weaker vs which is stronger. The table I listed in my last response is based on the spectrochemical series of colors. The order I listed is determined by what colors are formed by the complex(s); i.e., a coordination complex is formed, the absorption of light is mesured (even into the ultraviolet) and the order is determined from the wavelength absorbed. More energy is in the UV and less energy in the red and orange. Your original post asked, "Is chloride ion or water a stronger ligand?" The second question was similar and the same for the third. No where did the problem ask WHY. I have looked at my references at home and I can't find a WHY. I think it is a combination of size, electronegativity, dipole moments, and number of connecting sites on the ligand (en, for example, is a bidendate instead of a monodentate), just to name a few, but there may be others. That means memorizing the list from top to bottom or the reverse. I don't find anything that connects size, EN, dipole moment, etc to the strength of a ligand.