Fig. 5. Mechanistic study.

a Deuterium labeling experiments. b Inhibition of Z/E isomerization with an inert alkyne. c Kinetic trace of Z-selective products for reactions employing 1a, 9a, and mixture of 1a and 9a, respectively. Products of the mixed system have been marked in the profile. Reaction conditions: terminal alkyne (1.0 equiv, 0.4 mmol), HBpin (1.3 equiv), Co(acac)₂ ([Co], 0.5 mol%), CNC-ⁱPr (1.4 equiv to [Co]), ^tBuOK (5.6 equiv to [Co]) in DMF (0.5 ml) at room temperature (r.t.). d High Resolution Mass Spectrometry (HRMS) of [Co(II)(CNC-ⁱPr)Br]⁺. e X-ray structure of [Co(III) (CNC-ⁱPr)₂]Br₃. Hydrogen, bromine, and solvent atoms are omitted for clarity. See Supplementary Fig. 14 and Supplementary Tables 13–15 for details. f Proposed mechanism. The positions of the colored hydrogen atoms have been traced by the deuterium labeling experiments (a).