We have applied new methods for performing coupled‐cluster calculations to small molecules containing iodine atoms; specifically, NI3 and N2I4. Because NI3 is known to be very reactive, attempts to measure its thermodynamic properties have been challenging at best. To date, N2I4 has not been isolated, and our results suggest that its isolation will be just as challenging. We find that the ΔH f(NI3)=+307.7 kJ mol−1 and ΔH f(N2I4)=+551.6 kJ mol−1, confirming that they are unstable with respect to their decomposition products N2 and I2.