Tetracobalt dodecacarbonyl

Tetracobalt dodecacarbonyl is the chemical compound with the formula Co₄(CO)₁₂. It is a black crystalline compound that is insoluble in water and easily oxidized by air. It is an example of a metal carbonyl cluster.

Tetracobalt dodecacarbonyl

Names
Other names cobalt dodecacarbonyl, cobalt carbonyl
Identifiers
CAS Number	17786-31-1
3D model (JSmol)	Interactive image
ChemSpider	453122
ECHA InfoCard	100.037.951
EC Number	241-763-1
PubChem CID	519477
CompTox Dashboard (EPA)	DTXSID20939000
InChI InChI=1S/12CO.4Co/c12*1-2;;;; Key: YMFAWOSEDSLYSZ-UHFFFAOYSA-N
SMILES [Co-2]1235(C#[O+])(C#[O+])C(=O)[Co-2]246(C#[O+])(C#[O+])C(=O)[Co-2]34(C#[O+])(C#[O+])(C1=O)[Co-3]56(C#[O+])(C#[O+])C#[O+]
Properties
Chemical formula	Co4(CO)12
Molar mass	571.858 g/mol
Appearance	black crystal
Density	2.09 g/cm3
Melting point	decomposes at 60 °C (140 °F; 333 K)
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H228, H301, H317, H331, H351
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Synthesis and structure

This compound is synthesized by decarbonylation of Co₂(CO)₈.

2 Co₂(CO)₈ → Co₄(CO)₁₂ + 4 CO

The molecule consists of a tetrahedral Co₄ core, but the molecular symmetry is C_3v. Three carbonyl ligands are bridging ligands and nine are terminal.^[1] The average Co-Co distance is 2.499 Å, the average C-O bond length is 1.133 Å, and the average Co-C-O angle is 177.5°.^[2][3]

Rh₄(CO)₁₂ adopts the same C_3v structure but Ir₄(CO)₁₂ has perfect T_d symmetry with no bridging CO ligands groups.^[4] The Rh₄ and Ir₄ clusters are more thermally robust than that of the Co₄ compound, reflecting the usual trend in the strengths of metal-metal bond for second and third row metals vs those for the first row metals. There has been disagreement between the theoretically predicted and experimental structure of tetracobalt dodecacarbonyl.^[5][4][6]