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Shapes of complex ions

Cis-platin has the 'square planar' shape, whereas copper with four chlorides around it has a tetrahedral shape, according to a mark scheme I have. I don't understand why there is a difference or why the square planar shape occurs as I haven't encountered it before. Someone shed some light on complex ions with four monodentate ligands?

Much love :biggrin:

Reply 1

Dec S 92

I think you just have to remember that cis/trans-platin is an example of square planar, at A2 its not necessery to know why.

Reply 2

Kyri

You don't have to know why at A level, but its to do with the electronic configuration of Pt(II) vs Cu(II). The first is d8 and the second is d9 and this affects geometry. d8 metal centres with four ligands often form square planar complexes

(edited 13 years ago)

Thanks

As has been said, you don't need to know for A level. The reason square planar complexes occur is due to the way the metal d orbitals get lowered/raised in energy as a result of interactions with ligands. Different geometeries cause different arrangements of orbitals energy wise, and then the number of electrons you have to fill them with determines which configuration is adopted.

eg: