Dehydration and linkage isomerization in K4[Ni(NO2)6]-H2O

The dehydration of K₄Ni(NO₂)₆]-H₂O and the simultaneous linkage isomerization have been studied using differential scanning calorimetry. Two types of behavior were found for different samples. In one case, complete dehydration occurs and there is partial conversion of N-bonded nitrite to the O-bonded form. In the other case, only about 20% of the water is removed during the isomerization. The enthalpy change is estimated to be 3.5 kcal mol^?1 for each nitrite converted and 9.6 kcal mol^?1 for the dehydration.