Are ambidentate ligands considered different entities when they donate through different atoms? For example will a hypothetical square planar complex like [Pt(ONO)2(NO2)2] show geometrical isomerism?

  • $\begingroup$ i think you are right $\endgroup$ Commented Mar 24, 2019 at 6:50

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To specify [Pt(NO2)4]2+ would mean the ligand donates electrons through the N-atom, and not the O-atom. If it were to donate through O, it would be written as (ONO) and not (NO2).

Thus, this compound would not show geometrical isomerism. Also note that, if NO2 ligands are replaced by ONO, then that is a form of structural isomerism in complexes, called linkage isomerism.

  • $\begingroup$ Edited the complex to [Pt(NO2)2(ONO)2]. This doesn't answer my main question though, as to whether -ONO and -NO2 will be treated differently when considering stereoisomerism $\endgroup$
    – himanshu
    Commented Mar 26, 2019 at 12:31
  • $\begingroup$ If you write the complex as you have written now, then it does show geometrical isomerism. The point is, if a ligand is written as NO2 then it is nitrito-N and if it is written as ONO then it is nitrito-O. Similarly for other ligands (CN and NC are different, etc). Just like in organic chemistry, when discussing stereo isomers, don't count structural isomers. $\endgroup$ Commented Mar 27, 2019 at 7:12

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