How to determine dsp2 or sp3 structure?

[sachin123]

Taking an example as:
[CuCl4]^2- (charge =-2)
I finding it very confusing to decide whether the structure would be dsp2 or sp3?
There will 9 electrons in d orbital of Cu2+ in this compound.
In the presence of Cl- ligand will one electron get transferred to 4p orbital or will it stay in the 3d orbital?More importantly why would it behave so?
I just want a general rule so I won't have to mug up all the compounds.My textbook doesn't give any extra information.
Please help me out.
Thank you

 

[Nino MMP]

.The structure of [CuCl4]2- is sp3 because it has a tetrahedral coordination geometry. The four chlorine atoms occupy the four positions in the tetrahedron, and the copper ion is at the center. The nine electrons in the d orbital of Cu2+ will remain in the 3d orbital. The explanation for this is that the 3d orbitals are more stable than the 4p orbitals, so electrons prefer to stay in the 3d orbitals rather than being transferred to the 4p orbitals. This is a general rule that applies to most transition metal complexes.