Tetracobalt dodecacarbonyl
# Tetracobalt dodecacarbonyl

Tetracobalt dodecacarbonyl is the chemical compound with the formula $Co_4(CO)_{12}.$ 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.

## Synthesis and structure

This compound is synthesized by decarbonylation of $Co_2(CO)_8.$

    2 $Co_2(CO)_8$ → $Co_4(CO)_{12}$ + 4 CO

The molecule consists of a tetrahedral $Co_4$ core, but the molecular symmetry is $C_{3v}.$ Three carbonyl ligands are bridging ligands and nine are terminal. 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°.

$Rh_4(CO)_{12}$ adopts the same $C_{3v}$ structure but $Ir_4(CO)_{12}$ has perfect $T_d$ symmetry with no bridging CO ligands groups. The $Rh_4$ and $Ir_4$ clusters are more thermally robust than that of the $Co_4$ 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.

