N2 Dissociation vs Reversible 1,2-Methyl Migration in PCNHCP Cobalt(I) Complexes in the Stereoselective Isomerization (E/Z) of Allyl Ethers

With growing efforts pushing toward sustainable catalysis, using earth-abundant metals has become increasingly important. Here, we present the first examples of cobalt PC_NHCP pincer complexes that demonstrate dual stereoselectivity for allyl ether isomerization. While the cationic cobalt complex [((PC_NHCP)Co)₂-μ-N₂][BAr₄^F]₂ (3) mainly favors the Z-isomer of the enol ether, the corresponding methyl complex [(PC_NHCP)CoMe] (4) mostly gives the E-isomer. The dichotomy in selectivity was investigated computationally, revealing important contributions from the substituents on the metal (N₂ vs Me), including a 1,2-alkyl migration from cobalt to the N-heterocyclic carbene (NHC) of the methyl substituent, which is further explored in this report.