Advanced Topic 697 of 1102 Inorganic Chemistry
Metal Carbonyls
Complexes of CO with metals obeying the 18-electron rule, like Ni(CO)4.
In-depth explanation of Metal Carbonyls
Metal carbonyls are complexes in which carbon monoxide acts as a ligand, bonding to the metal through its carbon atom. The bonding is synergic: CO donates a lone pair into an empty metal orbital, and filled metal d electrons flow back into the empty pi antibonding orbitals of CO. This pi back-donation weakens the C-O bond, lowering its stretching frequency in infrared spectroscopy. Ni(CO)4 is tetrahedral, Fe(CO)5 is trigonal bipyramidal and Cr(CO)6 is octahedral. Many metal carbonyls obey the 18-electron rule.
Going deeper: Metal Carbonyls
Key ideas: Neutral complexes with CO ligands: Ni(CO)4 (tetrahedral), Fe(CO)5 (trigonal bipyramidal), Cr(CO)6 (octahedral), Mn2(CO)10 (M-M bond). Bonding: sigma donation from C lone pair to metal plus pi back-donation from filled d orbitals into CO pi* orbitals, which strengthens M-C and weakens C-O. IR C-O stretching falls from 2143 in free CO to about 1850 to 2100 cm-1 in complexes, lower for more back-donation or bridging CO.
Common mistakes and connections: Students think CO is a weak ligand because it is a poor base; back-bonding makes it strong. Metal is in low or zero oxidation state. Bridging carbonyls appear near 1800 cm-1. Compounds are toxic and volatile. Links to 18-electron rule, Mond process and spectroscopy.
Visualization of Metal Carbonyls
Carbon monoxide binds metals through its carbon atom, donating its lone pair while accepting back-donation into its pi-star orbitals. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Cr(CO)6 is a stable octahedral solid, while Ni(CO)4 is a volatile, highly toxic liquid.
Frequently asked questions about Metal Carbonyls
What is Metal Carbonyls?
Complexes of CO with metals obeying the 18-electron rule, like Ni(CO)4.
Is Metal Carbonyls a beginner, intermediate or advanced topic?
Metal Carbonyls is a advanced topic in Inorganic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Metal Carbonyls?
Study these earlier topics in Inorganic Chemistry first: Zone Refining, Mond Process, Organometallic Compounds.
What comes after Metal Carbonyls?
The next topics in Inorganic Chemistry are Eighteen Electron Rule and Ferrocene.
Can I practise Metal Carbonyls with quizzes?
Yes. The interactive lesson includes a self-check question on Metal Carbonyls, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Metal Carbonyls fits in Inorganic Chemistry
Metal Carbonyls is topic 82 of 113 in Inorganic Chemistry.