From my perspective these resonance structures allow these specific polyatomic ions to act as donor-acceptor molecules. Many donor-acceptor molecules also tend to be conjugated systems because they have chains of alternating conjugated π orbitals.

So does this imply that these ions (due to their resonance structures) can act as though they had a conjugated system or am I making too big of an assumption?

Curious on others perspectives/if I'm totally of my rocker.

  • $\begingroup$ I think you're a bit off ;) To my understanding, the IUPAC Gold Book restricts the term conjugation to organic chemistry. I'm highly biased and too much an organic chemist to disagree :D $\endgroup$ Jan 28, 2014 at 20:42
  • $\begingroup$ @Klaus Warzecha: If the OP substituted "delocalized" in place of "conjugated", would that make for a better statement? $\endgroup$
    – ron
    Jan 28, 2014 at 22:40
  • $\begingroup$ I appreciate the thoughts guys! I think what I'm hunting for is what lies in the stricter definitions of what makes something conjugated vs what makes something resonant. Though in both cases I would consider the electrons delocalized as @ron mentioned. Thanks guys! $\endgroup$
    – Sean
    Jan 29, 2014 at 23:01

1 Answer 1


"Conjugated" implies a 1,3-shift to move an electron or hole. It is a remnant of LCAO modeling that is obviously wrong but fantastically useful short of the Woodward-Hoffmann rules. I'm not sure inorganikers would like the name as such. MO modeling is accurate but unwieldly. "Delocalized" or "resonance hybrid" is good, certainly for inorganic systems that may have (virtual) d-orbital participation.

Consider nitrate. Inorganikers would say $\ce{N^{5+}}$, $\ce{^{-}O-N(=O)2}$, with five bonds to the nitrogen. The negative charge 1,3-shifts around all three oxygens. Organikers would see it as $\ce{N^{3+}}$, $\ce{[^{-}O{}-]_2N^{+}=O}%edit$, with four bonds to the nitrogen. 1,3 shifts, etc. Is nitrate ever a bidentate ligand? YES! But it is just another resonance structure.

Inorg. Chem. 35(24) 6964 (1996) http://pubs.acs.org/doi/abs/10.1021/ic960587b

  • 3
    $\begingroup$ Few people would really assign five bonds to nitrogen in nitrate ion. We can explain its characteristics with only four bonds. Yes the oxidation state is +5 -- consisting of +4 for four bonds to more electronegative atoms, and +1 more by sharing one more electron pair than the normal valence of three. $\endgroup$ May 28, 2016 at 9:32

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