Iridium forms compound in +9 oxidation state

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Posted by: Tarun Kumar
An international team of scientists has made a
compound containing iridium in the +9 oxidation
state – something that has been predicted by
theoretical models but never formed
experimentally before.
Until now, the highest oxidation state any element
was shown to exist at was +8. Iridium, with nine
valence electrons, can exist in a variety of
oxidation states – the most common under
normal conditions are +3 and +4. In 2009,
researchers made molecules of IrO – a form of
iridium oxide where iridium was formally in the +8
state, with an outer shell electron configuration of
5d . Subsequent theoretical models suggested the
last d-orbital electron could be 'removed' to
create a stable iridium oxide cation where iridium
could be counted as being in the +9 oxidation
state.
Now, a team led by Mingfei Zhou at Fudan
University in China have successfully formed the
[IrO ] cation in the gas phase using pulsed-laser
vaporisation of an iridium metal target, and
identified it using photodissociation spectroscopy.
The team also carried out calculations to predict
some of the salts [IrO ] might be able to form,
but have so far not managed to prepare any of
these.
REFERENCES
G Wang et al, Nature , 514 , 475 ( DOI: 10.1038/
nature13795 )