Whenever I try to find the number of geometrical isomers (including optical isomers) of coordination compound I got confused and mostly miss few isomers Is there any standard method to know the number of isomers of compounds such as Ma2b2c2 or [M(AA)a2b2].

where M is metal and a,b are modentate ligand whileAA are bidentate ligand .


Do it many times over, so as not to get confused.

Alternatively, there is a thing called Polya's formula, but you won't be able to use it anyway. In trivial cases like this, the said formula is about 100 times more complicated than counting isomers by hand. It is not before polysubstituted fullerenes that its use in chemistry starts making any sense.


For Ma2b2c2, you could go by:

  1. All cis (aCa) (bCb) (cCc)
  2. All trans (aTa) (bTb) (cTc)
  3. Only 1 trans (aTa)
  4. Only 1 trans (bTb)
  5. Only 1 trans (cTc)

Similar cases could be done for M(AA)b2c2, except of the fact that, (AA) will remain always cis [all cases EXCEPT where the 2 donor atoms are connected by NOT-A-VERY-LONG-CHAIN]

  • $\begingroup$ And how to know about optical activity $\endgroup$ – search Apr 22 '17 at 3:09

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