Metal carbonyl 18-electron complexes is sometimes catalysed by catalytic amounts of oxidants, via electron-transfer. Metal carbonyls react with reducing agents such as metallic sodium or sodium amalgam to give carbonylmetalate (or carbonylate) anions: For iron pentacarbonyl, one obtains the tetracarbonylferrate with loss of CO: Mercury can insert into the metal-metal bonds of some polynuclear metal carbonyls: The CO ligand is often susceptible to attack by nucleophiles. For example, trimethylamine oxide and bistrimethylsilylamide convert CO ligands to CO and CN, respectively. In the "Hieber base reaction", hydroxide ion attacks the CO ligand to give a metallacarboxylic acid, followed by the release of carbon
Mercury cycle the application of the European Directives 96/61/CE (Integrated pollution prevention and control) and 96/62/CE (Ambient air quality assessment and management) in which emission limits for toxic trace elements, such as mercury, are clearly established, energy production plants using coal must control mercury emissions. In January 2005, the European Commission adopted a mercury strategy for reducing mercury levels in the environment. Mercury cycle The mercury cycle is a biogeochemical cycle involving mercury. Mercury is notable for being the only metal which is liquid at room temperature. It is a volatile metal and evaporates, though it takes quite a while to do