[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??

[charco]

(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??

Rule of thumb: 4-coordinate = tetrahedral

Exceptions: some d8 complexes (PtCl₄, NiCl₄)