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Chelated O2BOH2- or Chelated O2CO2-: An Isoelectronic Conundrum
Fouad Ismael1, Cassandra L Fleming1, Lawrence R Gahan2
1Department of Chemistry, Auckland University of Technology, Private Bag 92006, Auckland 1142, New Zealand.
Inorganic Chemistry
|October 26, 2023
Summary
A cobalt(II) complex was re-identified as a cobalt(III) complex. This revision involved a change from a chelated O2BOH2- ligand to a chelated O2CO2- ligand, confirmed by multiple analytical techniques.
Area of Science:
- Inorganic Chemistry
- Coordination Chemistry
- Crystallography
Background:
- The initial characterization of a cobalt complex, reported as [Co(bipy)2O2BOH]·[B5O6(OH)4]·H3BO3·H3O·H2O, suggested a Cobalt(II) oxidation state with a chelated O2BOH2- ligand.
- This complex was a subject of interest due to its unique ligand structure and potential applications in coordination chemistry.
Purpose of the Study:
- To re-evaluate and accurately determine the structure and oxidation state of the cobalt complex previously reported.
- To clarify the nature of the chelated ligand within the cobalt coordination sphere.
Main Methods:
- Spectroscopic analysis including 1H and 13C Nuclear Magnetic Resonance (NMR), Mass Spectrometry (MS), and Infrared (IR) spectroscopy.
- X-ray crystallography was employed to obtain a definitive structural determination.
Main Results:
- The cobalt complex was accurately identified as [Co(bipy)2O2CO]·[B5O6(OH)4]·H3BO3·2H2O.
- The central cobalt atom is in the Cobalt(III) oxidation state.
- The ligand was confirmed to be a chelated O2CO2- (carbonate) ligand, not O2BOH2-.
Conclusions:
- The original structural assignment of the cobalt complex was incorrect.
- The correct structure features a Cobalt(III) ion coordinated to a chelated carbonate ligand, fundamentally altering the understanding of this coordination compound.
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