Results are out! Find what you need...fast. Get quick advice or join the chat
Hey there Sign in to join this conversationNew here? Join for free

Chelates!

Announcements Posted on
Complete this short survey for a chance to win an iPad mini! 22-09-2014
    • Thread Starter
    • 1 follower
    Offline

    ReputationRep:
    Just wondering if anyone could tell me why chelates are more stable than complexes containing unidendate lingands. Also, why are metal (III) chelates more stable than metal (II) chelates?

    Thanks alot for any help!
    • Thread Starter
    • 1 follower
    Offline

    ReputationRep:
    Oh are they more stable because their formation involves an increase in entropy? I'm still not sure about the other bit though!
    • 4 followers
    Offline

    ReputationRep:
    Because:

    M(H20)6 2+ + 3en ---> M(en)3 2+ + 6H2O

    i.e. 4 to 7 species, therefore increase in entropy is highly favourable.



    Regarding the other point, I think it's just basic electrostatics. If you're pairing M(III) with say an edta 4- hexadentate ligand, then pure electrostatic attractions will be stronger when the metal is in the higher oxidation state.
    • 22 followers
    Offline

    ReputationRep:
    (Original post by anna123)
    Just wondering if anyone could tell me why chelates are more stable than complexes containing unidendate lingands. Also, why are metal (III) chelates more stable than metal (II) chelates?

    Thanks alot for any help!
    As the other posters say - entropy...

    .. but there is also the logical contribution from statistical likelihood of collision.

    A multidentate complex may lose bonding from one ligand position, but the other bonds maintain the detached atom with a potentially bonding lone pair in the same spacial region increasing its likelihood of re-attachment.
    • Thread Starter
    • 1 follower
    Offline

    ReputationRep:
    Ok thank you both very much for your help!
    • 4 followers
    Offline

    ReputationRep:
    Entropy is the major driving force but enthaply plays a role.... If the ligands are charged, then there is a disfavourable interaction in bringing the multiple negatively charged ligands in close proximity to each other. In an equivalent charged chelate, these charges are already close together, hence enthalpy is more negative

Reply

Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. By joining you agree to our Ts and Cs, privacy policy and site rules

  2. Slide to join now Processing…

Updated: June 1, 2012
New on TSR

'Stalking pages' have changed!

Find other uni applicants with University Connect

Article updates
Reputation gems:
You get these gems as you gain rep from other members for making good contributions and giving helpful advice.