Stronger Ligand Chloroamine vs ammonia

[labqi]

Hey guys,
I was going through the questions in TPR Hyperlearning Science workbook. I got to Chemistry passage 25, question 2. I had trouble understanding it. I don't understand why chloroamine would be a stronger ligand than ammonia. It doesn't make sense to me considering the fact that a ligand is something that donates an electron pair. With chlorine being present, as an electron withdrawer/higher electronegativity, how could it be a stronger ligand? wouldn't it want to the keep the electrons for itself?

Thanks again.

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[labqi]

bump!

 

[swivelj]

Gonna put a guess out there, that do due to the halogen being an electron withdrawer that the bonds to H and bonds formed by the lone pair are held closer to the nitrogen, making them stronger. The bonds in NH3 withdraw no electron density so when the lone pair is donated it wouldn't be as strong as the lone pair donation of chloroamine. That's all got maybe someone else can weigh in?

 

[AKMCAT]

Thats weird. I would think its NH3 also since ligands are usually Lewis bases. and NH3 would be a stronger lewis base vs chloroamine.

 

[betterfuture]

Bump because I have the same confusion on this question.

Chlorine is an electronwithdrawing group so it would draw in electron density towards itself so why the opposite?

 

[aldol16]

I believe at the level of general chemistry, you can consider chloroamine to be a weaker ligand because of reduced Lewis basicity. The question may simply be incorrect. At a higher level, it's possible that the chlorine can withdraw electrons via a pi system, allowing the metal to backbond to the nitrogen and make the M-N bond stronger, but that is beyond the scope of the MCAT.