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Homework Help: Metal complexes - 18electron rule and LFSE.

  1. Oct 19, 2012 #1
    The nitro ligand creates a stronger ligand field than the nitrito ligand because

    a. O is more electronegative than N

    b. the O atom can be a π-acceptor

    c. the metal-N bond is shorter

    d. the N atom can be a π-acceptor

    e. b and d

    I ruled out B and therefore E, since oxygen is a pi donor atom. Both ligands contain two Os and one N, both are 2+ charged. The only thing I can think of that would result in higher ligand field is forming shorter bonds. Is the answer therefore C?

    The complex trans-diaquaporphyrinatomanganese(III) ion has a magnetic moment of 4.9 B.M. Jahn-Teller distortion is not observed in this complex because

    a. the porphyrin is a macrocyclic ligand

    b. water is a weak-field ligand

    c. there is no degeneracy in the eg* orbitals

    d. it is low-spin d4

    e. it is high-spin d4

    macrocycles form very stable bonds, they create a large splitting and therefore force the Mn(III) into a low spin configuration, is the answer then E or A or C, since all of them result in the same thing.

    The 18-electron rule applies to

    a. square-planar Pt(II) complexes

    b. octahedral Ni(II) complexes

    c. only metal carbonyl complexes

    d. high-spin complexes

    e. strong-field ligand complexes

    Square planar complexes follow 16e rule. Octahedral Ni(II), that would be more then 18 electrons. Can not be C, since ligands other then CO form 18 electron complexes, must be E? Since strong ligands force the eg orbitals out of range for electrons

    Help is much appreciated.
    Last edited: Oct 19, 2012
  2. jcsd
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