When heated to 700 °C, indium(III) oxide forms InO, (called indium(I) oxide or indium suboxide), at 2000 °C it decomposes.
It is soluble in acids but not in alkali.
With ammonia at high temperature indium nitride is formed:
: InO + 2 NH → 2 InN + 3 HO
With KO and indium metal the compound KInO containing tetrahedral  InO ions was prepared.
Reacting with a range of metal trioxides produces perovskites for example:
:InO + CrO → 2InCrO