Alkyne Semihydrogenation with a Well-Defined Nonclassical Co-H 2 Catalyst: A H 2 Spin on Isomerization and E-Selectivity

The reactivity of a Co -H complex was extended toward the semihydrogenation of internal alkynes. Under ambient temperatures and moderate pressures of H , a broad scope of alkynes were semihydrogenated using a Co -N precatalyst, resulting in the formation of trans-alkene products. Furthermore, mechanistic studies using H, H, and para-hydrogen induced polarization (PHIP) transfer NMR spectroscopy revealed cis-hydrogenation of the alkyne occurs first. The Co-mediated alkene isomerization afforded the E-selective products from a broad group of alkynes with good yields and E/Z selectivity.