text: Metal carbonyl hydrides are used as catalysts in the hydroformylation of olefins. The catalyst is usually formed in situ in a reaction of a metal salt precursor with the syngas. The hydroformylation starts with the generation of a coordinatively unsaturated 16-electron metal carbonyl hydride complex like HCo(CO) or HRh(CO)(PPh) by dissociation of a ligand.  Such complexes bind olefins in a first step via π-complexation, thus beginning the transformation of the alkene to the aldehyde.
  Iron carbonyl hydrides occur in nature at the active sites of hydrogenase enzymes.