4[Co2(CO)8] + 8NaOH → 4[Co(CO)4H] + [Co4(CO)12] + 4Na2CO3
Oktacarbonyldicobalt react with sodium hydroxide to produce hydroxotetracarbonylcobalt, dodekacarbonyltetracobalt and sodium carbonate. Sodium hydroxide - diluted solution. This reaction slowly takes place at a temperature near 0°C.