The effect of Co and Ir on the ammonia synthesis over the K-2[Fe-2(CO)(8)] + K and K-2[Ru-4(CO)(13)] + K catalysts on graphite-like active carbon "Sibunit" has been investigated. The catalysts were prepared by depositing K-2[Fe-2(CO)(8)] and K-2[Ru-4(CO)(13)] onto the "Sibunit" carbon-supported Co and Ir, followed by thermal decomposition of the deposited cluster and treatment of the resulting sample with metallic potassium. The catalysts containing no potassium metal have been studied as well. It has been found that the presence of Co in the Ru catalysts substantially decreases the ammonia synthesis rate. Similar results have been obtained on testing the Ru-Ir samples. By contrast, the introduction of Ir in the K-2[Fe-2(CO)(8)] + K catalysts leads to a synergistic acceleration of the process of the ammonia synthesis. The strongest accelerating effect of Ir is observed at 200 degreesC, A rise in the reaction temperature to 250, 300 and then to 350 degreesC results in a gradual weakening of the Fe-Ir synergism, An important feature of the Fe-Ir catalysts found is their increased activity in the ammonia synthesis at 150 degreesC, The presence of Co in the iron catalysts little affects, in general, the ammonia synthesis rate, although some acceleration of this process by Co at 350 and 400 degreesC for the samples not treated with potassium metal can be noted.