Since the discovery of the first homoleptic metal carbonyl complex Ni(CO)4 more than 130 years ago, scientists try to obtain further such compounds formed from a carbon monoxide molecule and a metal that are important for basic research as well as applications. The last new compound of this type to be bottled, the Co(CO)5 cation, was reported in 2003. However, extensive research in the gas phase has shown that far more metal carbonyl complexes than those known to date should exist, including the chromium hexacarbonyl cation.