The present disclosure relates to a bridging asymmetric haloalkynyl dicobalt hexacarbonyl precursors, and ultra high purity versions thereof, methods of making, and methods of using these bridging asymmetric haloalkynyl dicobalt hexacarbonyl precursors in a vapor deposition process. One aspect of the disclosure relates to an ultrahigh purity bridging asymmetric haloalkynyl dicobalt hexacarbonyl precursor of the formula Co2(CO)6(R3C≡CR4), where R3 and R4 are different organic moieties and R4 is more electronegative or more electron withdrawing compared to R3.