# Determining geometry of coordination compund without experimental data [closed]

How can I determine if a coordination compound has a tetrahedral or square planar geometry without any experimental data (such as magnetic spin) by just looking at its formula?

For example, what is the geometry of the following complexes:

• $$\ce{[CoCl4]^2-}$$
• $$\ce{[Ni(CN)4]^2-}$$
• $$\ce{[CuCl4]^2-}$$

Do they have a Jahn-Teller distortion?

• Your question is like asking "how do I tell whether an object weighs more than a kilogram without measuring its mass". For some objects, it's obvious: a feather is definitely under 1 kg, an elephant definitely over. For some other things, your eyes aren't good enough and the only way to know is to put it on a scale. A more nuanced question, and probably better, would be to ask what factors tend to favour tetrahedral geometries vs square planar geometries. Some of them are touched upon here: chemistry.stackexchange.com/q/40880/16683 – orthocresol Jun 27 '19 at 13:51
• Thank you for your time. I know that question is a bit odd but this is a question from my last inorganic chemistry exam. Well, let me write that question exactly, Wich one of those ligands you can observe Jahn-Teller Distortion? and why? [CoCl4]2− [Ni(CN)4]2− [CuCl4]2− – İsmail Burak AYDIN Jun 27 '19 at 15:59