Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Ammonia is a strong or weak field ligand?

  1. Sep 1, 2018 #1

    Wrichik Basu

    User Avatar
    Gold Member

    Ammonia is present in the spectrochemical series near the middle, just after water. Is it a strong field ligand, or a weak field ligand?

    Also, take into consideration the complex ##[Ni(NH_3)_4 Cl_2]##. Chloride ion is towards the left end of the spectrochemical series which means it is a weak field ligand. Will the complex be a high spin or a low spin one?
     
  2. jcsd
  3. Sep 3, 2018 #2

    TeethWhitener

    User Avatar
    Science Advisor
    Gold Member

    Draw out the d-orbital configurations for Ni(II) high spin and low spin. What do you notice?
     
  4. Sep 3, 2018 #3

    Wrichik Basu

    User Avatar
    Gold Member

    Ni(II) has 8 electrons in its 3d-orbital.

    For low-spin complex:
    ##t_{2g}: d_{xy}^2 \, d_{yz}^2 \, d_{xz}^2##
    ##e_g: d_{x^2-y^2}^2 \, d_{z^2}^0##

    For high-spin complex:
    ##t_{2g}: d_{xy}^2 \, d_{yz}^2 \, d_{xz}^2##
    ##e_g: d_{x^2-y^1}^2 \, d_{z^2}^1##

    What conclusion can I draw from these?
     
  5. Sep 4, 2018 #4

    mjc123

    User Avatar
    Science Advisor

    Not that high-spin Ni(II) has nine d electrons, certainly.
     
  6. Sep 4, 2018 #5

    TeethWhitener

    User Avatar
    Science Advisor
    Gold Member

    Also remember Hund’s Rule.
     
  7. Sep 4, 2018 #6

    Wrichik Basu

    User Avatar
    Gold Member

    My mistake. Corrected ones:

    For low-spin complex:
    ##t_{2g}: d_{xy}^2 \, d_{yz}^2 \, d_{xz}^2##
    ##e_g: d_{x^2-y^2}^1 \, d_{z^2}^1##

    For high-spin complex:
    ##t_{2g}: d_{xy}^2 \, d_{yz}^2 \, d_{xz}^2##
    ##e_g: d_{x^2-y^1}^1 \, d_{z^2}^1##

    Both are same. Understood. Thanks @TeethWhitener

    What about the first question:

     
  8. Sep 4, 2018 #7

    TeethWhitener

    User Avatar
    Science Advisor
    Gold Member

    Yes. For d0 through d3 and d8 through d10, there's really only one way to fill the d orbital states (EDIT: this is only true for octahedral complexes--once the geometry changes, the rules change), so high-spin vs. low-spin isn't a factor.
    One way to do this is to look at a case where the spin states do matter (d4 through d7) and see whether the ammine complexes are low-spin or high-spin. Looking at hexamminecobalt(III), you have a d6 cobalt center that's octahedral and low-spin, so this suggests that NH3 is a reasonably strong field ligand.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted