Cobalt tetracarbonyl hydride is an organometallic compound with the formula HCo(CO)4. It is a volatile, yellow liquid that forms a colorless vapor and has an intolerable odor. The compound readily decomposes upon melt and in absentia of high CO partial pressures forms Co2(CO)8. Despite operational challenges associated with its handling, the compound has received considerable attention for its ability to function as a catalyst in hydroformylation. In this respect, HCo(CO)4 and related derivatives have received significant academic interest for their ability to mediate a variety of carbonylation reactions.