Complexes - why square planar?

xarcul

Why do some metal complexes exist as square planar molecules, for example cisplatin?

Nice short question! :p:

Thanks!

Reply 1

shengoc

xarcul

Why do some metal complexes exist as square planar molecules, for example cisplatin?

Nice short question! :p:

Thanks!

A nice short question that takes quite a long time to explain.
It is to do with energy(ligand field stabilisation energy). For TM complexes, two models are often applied:
1) crystal field theory - based on electrostatic repulsion between central TM and the ligands
2) ligand field theory - based on molecular orbital arguments

To be general(at this point), it is most common for d8 TM complex to be square planar especially the 4d and 5d; only one exception that is PdF4 which adopts the rutile TiO2 structure.

3d8 Ni however could choose tetrahedral or square planar depending on the ligand(size).

cis platin has Pt(II) which is 4d8 so it is selectively square planar as that will maximise its LFSE.

Reply 2

charco

Study Forum Helper

xarcul

Why do some metal complexes exist as square planar molecules, for example cisplatin?

Nice short question! :p:

Thanks!

Because they are more stable that way!

Nice short answer :biggrin:

Reply 3

shengoc

lol, i am overcomplicating stuff for a poor a level student who would be so shocked at university chemistry!

Reply 4

Kyle_S-C

xarcul

Why do some metal complexes exist as square planar molecules, for example cisplatin?

Nice short question! :p:

Thanks!

No idea if this is true (and my brain is currently in no shape to work it out), but it looks pretty good...

http://en.wikipedia.org/wiki/AXE_method#AXE_Method

Reply 5

shengoc

Kyle_S-C

No idea if this is true (and my brain is currently in no shape to work it out), but it looks pretty good...

http://en.wikipedia.org/wiki/AXE_method#AXE_Method

nothing seems short in uni questions