[en] Relaxation times T1 and the NMR line second moment are measured vs temperature in cobalt hexaammino-iodide. The temperature-dependence of T1 served to determine the activation energy for tumbling motion of the complex cation and that of motion of the NH3 groups. At Tsub(c)=2800K, a jump in T1 is observed pointing to a phase transition. The results for the second moment confirm the conclusions drawn from longitudinal relaxation investigation. (author)