Four (binap)(enyne)tetracarbonyldicobalt(0) complexes have been synthesised and their reactivity monitored by variable temperature (31)P NMR spectroscopy. Formation of (binap)dicarbonylhydridocobalt(-1) 12 occurred at temperatures between 35 and 55 degrees C, depending on the nature of the alkene and alkyne components of the enyne. The structure of 12 was determined by X-ray crystallography, and its presence under Pauson-Khand reaction conditions was verified by NMR spectroscopy.