Metal carbonyl

A coordination compound containing carbon monoxide ligands bonded to a metal atom or ion. Metal carbonyls are distinguished by metal-to-CO bonding that includes donation from the metal into carbon monoxide’s antibonding orbitals.

Synergic bonding: A bonding model in which ligand-to-metal donation and metal-to-ligand back-donation reinforce each other. Carbon monoxide binds through paired σ donation and π back-donation.
Carbon monoxide: A colorless, toxic gas consisting of one carbon atom triple-bonded to one oxygen atom. It is the ligand whose binding defines a metal carbonyl.
Mond process: An industrial process that purifies nickel by converting it to volatile nickel tetracarbonyl and then decomposing it. Nickel tetracarbonyl volatility enables nickel purification through carbonyl formation and decomposition.
Iron pentacarbonyl: A volatile iron compound with five carbon monoxide ligands and the formula Fe(CO)5. Its trigonal-bipyramidal structure is a standard example of a mononuclear carbonyl.
Metal nitrosyl: A coordination compound containing nitric oxide bonded to a metal center. Nitric oxide resembles CO as a π-acceptor ligand but has distinct electron-counting behavior.
π backbonding: Donation of electron density from a filled metal orbital into an empty ligand antibonding orbital. Back-donation weakens the CO bond and lowers its stretching frequency.
Ligand: An ion or molecule that donates electron density to a central atom, commonly a metal. CO acts as a ligand by donating a lone pair to the metal.
Hydroformylation: An industrial reaction that adds carbon monoxide and hydrogen to alkenes to form aldehydes. Cobalt and rhodium carbonyl species catalyze this major route to aldehydes.
Chromium hexacarbonyl: A chromium compound with six carbon monoxide ligands and the formula Cr(CO)6. Its octahedral structure illustrates a highly symmetric 18-electron carbonyl.
Metal hydride: A compound containing hydrogen bonded directly to a metal. Hydride ligands differ from CO in charge, bonding, and effects on metal electron density.

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