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
Barbier reaction aqueous ammonium chloride solution added later to quench the reaction): the intramolecular Barbier reaction with samarium(II) iodide: the reaction of an allyl bromide with formaldehyde in THF with indium powder: or another allyl bromide in a reaction with benzaldehyde and zinc powder in water: The synthesis of (+)-aspicillin, starts first with a hydroboration, then transmetallation to zinc which can then do an addition into the aldehyde substituent. Barbier reaction The Barbier reaction is an organometallic reaction between an alkyl halide(chloride, bromide, iodide), a carbonyl group and a metal. The reaction can be performed using magnesium, aluminium, zinc, indium, tin, samarium,