Sodium tetracarbonylcobaltate is the organocobalt compound with the formula NaCo(CO)4. It is a common derivative of the tetracarbonylcobaltate anion, [Co(CO)4]-, although several other alkali metal salts are known. The tetracarbonylcobaltate anion is the conjugate base of cobalt tetracarbonyl hydride, HCo(CO)4. According to X-ray crystallography, the Co(CO)4- center is nearly tetrahedral (isoelectronic with Ni(CO)4).
Conventionally, this compound is prepared by reduction of dicobalt octacarbonyl with sodium amalgam:
It reacts with mercuric cyanide to give a HgCo2 derivative:
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