Tetracobalt dodecacarbonyl explained

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.

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]}

References

1. Chini, P.. The closed metal carbonyl clusters . . 1968 . 2 . 31–51. 10.1016/0073-8085(68)80013-0.
2. Farrugia, L. J. . Braga, D. . Grepioni, F. . A structure redetermination of Co₄(CO)₁₂: evidence for dynamic disorder and the pathway of metal atom migration in the crystalline phase . . 1999 . 573 . 1–2 . 60–66. 10.1016/S0022-328X(98)00879-1.
3. Corradini, P.. Structure of tetracobaltdodecarbonyl . . 1959 . 1676–1677 . 31. 6 . 10.1063/1.1730674. 1959JChPh..31.1676C.
4. Wei, C. H. . Structural analyses of tetracobalt dodecacarbonyl and tetrarhodium dodecacarbonyl. Crystallographic treatments of a disordered structure and a twinned composite. . . 1969 . 8 . 11 . 2384–2397. 10.1021/ic50081a030.
5. Corradini. Paolo. Structure of tetracobaltdodecarbonyl. Journal of Chemical Physics. 1959. 31. 6. 1676–1677. 10.1063/1.1730674. 1959JChPh..31.1676C.
6. Farrugia. Louis J.. Braga. Dario. Grepioni. Fabrizia. A structure redetermination of Co₄(CO)₁₂: Evidence for dynamic disorder and the pathway of metal atom migration in the crystalline phase. Journal of Organometallic Chemistry. 1999. 573. 1–2. 60–66. 10.1016/S0022-328X(98)00879-1.