The concept of oxidation state (OS) is based on the concept of Lewis electron pairs, in which the bonding electrons are assigned to the more electronegative element. This approach is useful for keeping track of the electrons, predicting chemical trends, and guiding syntheses. Experimental and quantum-chemical results reveal a limit near +8 for the highest OS in stable neutral chemical substances under ambient conditions. OS=+9 was observed for the isolated [IrO4]+ cation in vacuum. The prediction of OS=+10 for isolated [PtO4]2+ cations is confirmed computationally for low temperatures only, but hasn't yet been experimentally verified. For high OS species, oxidation of the ligands, for example, of O−2 with formation of .O−1 and O−O bonds, and partial reduction of the metal center may be favorable, possibly leading to non-Lewis type structures.
Bibliographical noteFunding Information:
We thank Professors Jeremy Harvey and Martin Kaupp for illuminating discussions. W.H.E.S. thanks the Theoretical Chemistry Center of THU for hospitality and support. J.L. acknowledges the NSFC (grant nos. 21590792, 21433005, and 91426302) for financial support. S.X.H. acknowledges the NSFC (grant no. 21701006), the Foundation of the President of the Chinese Academy of Engineering Physics (grant no. YZJJSQ2017072), and the NASF (grant no. U1530401) for support. M.Z. was supported by the NSFC (grant no. 21433005). J.K.G. was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Heavy Element Chemistry Program at Lawrence Berkeley National Laboratory under Contract DE-AC02-05CH1123. The work in Minnesota was supported in part by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0015997. J.M. thanks the FundaÅ¼o para a CiÞncia e a Tecnologia (Portugal) for financial support through project UID/Multi/04349/2013 and RNEM – Portuguese Mass Spectrometry Network.
- bonding theory
- computational chemistry
- oxidation states
- transition metals