Crabtree, R. H. (2009). The Organometallic Chemistry of the Transition Metals (5ª edición). Hoboken, NJ: John Wiley and Sons. p. 2. ISBN 978-0-470-25762-3. «An industrial application of transition metal organometallic chemistry appeared as early as the 1880s, when Ludwig Mond showed that nickel can be purified by using CO to pick up nickel in the form of gaseous Ni(CO)4 that can easily be separated from solid impurities and later be thermally decomposed to give pure nickel.... Recent work has shown the existence of a growing class of metalloenzymes having organometallic ligand environments – considered as the chemistry of metal ions having C-donor ligands such as CO or the methyl group».