Alkyne Semihydrogenation with a Well-Defined Nonclassical Co–H₂ Catalyst: A H₂ Spin on Isomerization and <i>E</i>-Selectivity

Abstract

The reactivity of a Co^I-H₂ complex was extended toward the semihydrogenation of internal alkynes. Under ambient temperatures and moderate pressures of H₂, a broad scope of alkynes were semihydrogenated using a Co^I-N₂ precatalyst, resulting in the formation of trans-alkene products. Furthermore, mechanistic studies using ¹H, ²H, 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.