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shapes of complex ions

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    Is there any CORRECT way of deciding whether a complex ion of coordination no. 4 will have a square planar or a tetrahedral structure?


    I read in my book the shape of a complex ion, with 4 (unidentate) ligands, depends on whether the d orbitals are complete or not.

    Then it states, a transition metal with a coordination no. of 4, and a COMPLETE d subshell has a tetrahedral structure- and it uses cobalt as an example.

    How does Cobalt have a complete d-subshell?? Co---> [Ar] 3d7 4s2
    Co^(2+)---> [Ar] 3d7
    Co^(3+)---> [Ar] 3d6

    Is there a discrepancy or am I just high??
    :confused:
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    (Original post by poopypie)
    Is there any CORRECT way of deciding whether a complex ion of coordination no. 4 will have a square planar or a tetrahedral structure?


    I read in my book the shape of a complex ion, with 4 (unidentate) ligands, depends on whether the d orbitals are complete or not.

    Then it states, a transition metal with a coordination no. of 4, and a COMPLETE d subshell has a tetrahedral structure- and it uses cobalt as an example.

    How does Cobalt have a complete d-subshell?? Co---> [Ar] 3d7 4s2
    Co^(2+)---> [Ar] 3d7
    Co^(3+)---> [Ar] 3d6

    Is there a discrepancy or am I just high??
    :confused:
    Rule of thumb: 4-coordinate = tetrahedral

    Exceptions: some d8 complexes (PtCl4, NiCl4)

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Updated: March 30, 2012
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