# Is there a way to determine if a compound is oxygen or water sensitive?

The synthesis of $\ce{CoH[P(OPh)3]4}$ requires the use of an inert atmosphere e.g. nitrogen as the compound is air-sensitive. Is there any way to tell whether it is the oxygen or water vapour in the air specifically? I thought it might be water sensitive seeing as metal hydrides are basic and may therefore react in an acid-base reaction:

$$\ce{CoH[P(OPh)3]4 + H2O ⟶ Co[OH][P(OPh)3]4 + H2}$$

Is rationalisation correct/is there more to it than this?

• selectively expose it to pure oxygen or pure water and you will know whether only one of those is a problem. – matt_black Mar 20 '18 at 21:33

• Due to the relatively low oxidation state of $$\ce{Co(I)}$$ in the compound which will react with $$\ce{O2}$$ towards formation of $$\ce{Co(II)}$$.
• The $$\ce{P^{III}(OPh)3}$$ ligand is air sensitive as well and can oxidize to $$\ce{OP^V(OPh)3}$$ as well as reacting with water: https://www.alfa.com/en/catalog/A18662/.